I'm...a little bit confused as to why you would think that they're a scam?
Adoptables, from my point of view, is not really buying the drawing but rather the design. I know people whose strength isn't in character design and would rather pay to have someone's already made design (that might, for example, really match that idea for a character they had but couldn't think of clothes/hair/face for).
Lmao no? Buying an adoptable is just buying a design/character the artist has put effort into. They can price them whatever they want as designing also takes a lot of time, trial and error! You don't have to buy if you think they're too expensive. Sure, sometimes an artist's terms of service can be a bit shady and there's also thieves who sell stolen characters, but that definitely does not apply to the entire community of adopt sellers and buyers.
I see no reason whatsoever to buy adopts, but yeah, unless the author resells one adopt over and over again, it's not a scam, just selling a particular character design 
They aren't scams.
You can argue about the prices of adoptables that are basically just colored bases. But in the end, it's always an artistic effort and an interllectual property they offer you. I have barely ever go a basic adoptable go for any higher than 30$.
They are actually very useful bc a lot of people can't design their own characters, can't draw or dont have the creativity to think up a design themselves. Then adoptables are a blessing bc you can just look through a catalogue of characters and buy one to your liking. I have done that several times.
Esp. in the furry community adoptables are very popular.
Having followed the adopts community, albeit more from the outside than in, there are a few scammy folks who steal and sell designs but the majority I've seen are honest folks putting large amounts of work into creating character design from the ground up sometimes with story/background or other traits included and buyers can do with that what they will.
I'm wondering if the higher priced ones your seeing are coming out of the furry community or from adopt sellers who follow a bid based selling model, which yes will reach pretty high prices (sometimes even the hundreds). A lot of these designs though can be very detailed, maybe even ornamental, designs that require lots of time and effort to put together so to say "that's to much" is pretty dismissive.
Also with regards to the use of bases some folks will buy bases to use to make adopts, per the creator of the bases terms, and then it goes right back to time and labor constructing a unified design to go on top. I've even seen adopt designers create their own base to work from so that less time is spent structuring poses or body shapes and so on and can be directed to the actual design side.
I've personally seen folks who do themed adopts or character adopts based within certain fandoms (in my case sonic) and to make cohesive designs that look good again takes time and effort. At the end of the day though it's really between customer and client. Someone wants a character design and those folks are offering. A need exists, they provide, transactions happen and in most cases each party is fine with the result. I've even bought adopts myself, albeit years ago, but I see no issue with it.
I think it's fine to say "I don't like this thing" but to go and call folks scammers and thieves is kinda low especially when referring to an entire group as a whole. And granted people can have bad experiences but that doesn't mean paint an entire community as evil.
I never particularly understood the whole adopt biz. if you are wanting to have a design for your commercial something, wouldn't it be better to just commission the artist directly to do a character design for you, with the ability to have some degree of steering the artist's designing progress to be better tailored to your needs? And if you want to use it personally and non-commercially, nothing will stop you from just, dunno, right-clicking on the image that fancies you and saving it? I guess adopts are held together by the community interested in the core idea of selling characters around. Which... is uncomfortably close to a sort of slavery by my tastes. Yes, they aren't real people, but you are supposed to view them as if they were real, that's the whole point of a fictional character.
Then again, I view the very idea of being able to sell away your IP rights away as wrong. Those should be inalienable. Yours is yours forever, nobody should be able to coerce or convince you to give up what's basically your thoughts.
Okay now there is SO much wrong with this where do I even begin
yeah sure you could just steal a character. no one can stop you. but it's theft. you cant just steal a design that's up for sale. if the theft gets busted you'll be shunned from the art communities forever. sure there are people who do it but. you should NEVER do it. It's about ethics. YKnow, technically when you're on a market and no one sees it, you can just steal fruits. It's still theft.
yes for commercial use you probably dont want an adoptable, but why would a privat user always have to go to the issue of always coming up with a design themselves? A lot of people enjoy having characters, but are absolutely helpless when it comes to thinking of a design to explain to an artist to design, which is why adoptables can be very useful. I for example, once looked for a Bunny character, but thats all I had in mind, that its a bunny. no color, no markings, no clothes, no hair, nothing. So I looked for adoptables of bunny characters and found sth I enjoyed. Also sidenote: commissioning an artist to design you a character from scratch can be HEAPS more expensive than just buying an adoptable.
dont??? compare??? selling and trading fictional characters???? with slavery???????? this is absolutely wrong and you should never say sth of the likes of this. dont compare an absolute despicably real life human tragedy to the selling of a bunch of pixels. it is NOT comparable. characters dont have feelings, they aren't people, they dont care if they're being sold. get that mindset off IMMEDIATLY
if you dislike the thought of selling your IP rights away then in your opinion I should be jobless, right? I work for an advertisement agency, and we sell creative ideas all the time. Because. as I said. not everyone has the creative capacity to think of their own original ideas, and thats okay. thats why artists and media designers and that kind exist.
We exist to bring ideas to life.
If you yourself are capable of making up all of your designs 100% yourself thats great, you do you! But in no way shape or form does it make adoptable sellers "immoral" or "wrong" and it is not even in the SLIGHTEST comparable to sth as horrible as slavery.
Seconding all of the points that @Flauschwurm already brought up. But apart from the gross as all comparison it's worth remembering that major corporations buy and sell IPs ALL THE TIME. Look at Disney. Am I a fan of the way they're monopolizing, absolutely not but as they have the finance it's within their right as the law presently stands.
Also it's amazing how comfortable people are with the old "right click and save" as if there aren't artists all throughout our community and on the platforms we post making art. So if someone were to take your own work. Something that you've put time and effort into would your thoughts and feelings be the same? and I ask this as a genuine question, not to be antagonizing or combative despite how my tone likely reads by this point.
Lastly, most people who are selling adopts aren't doing so unwillingly. Often times these are characters or character designs they're no longer attached to or have made for the express purpose of selling them. I myself am considering doing this with a handful of designs that I literally have no use for. So it's not as though anyone is holding them at gunpoint demanding they hand over these design or else. It's literally just the same as any kind of vendor offering a product or service, selling something to their target audience.
Which ties back to the closing point of my first reply "you're free to dislike a think but don't go bashing it or making sweeping assumptions unless it's genuinely malicious" period.
I do it, you do it, everybody does it, whenever it's conscious or not. Every "original" idea is built on the foundation of previous experiences, and I "steal" the design of somebody's OC the nanosecond the photons from the monitor reach my retinas. Sadly, you cannot "unsee" things, or guarantee that they won't influence your own designs later on. But I guess you were talking about plagiarism? No, that's whole different issue, and yes, I absolutely do not support it in any way either, plagiarists are scumbags.
And people who steal OCs for personal use, I don't think they would care that they're shunned by the art communities forever, since they were'nt a part of it from the beginning. Somebody needs an avatar for their private roleplaying game session, so they go on the google and grab the first picture that strikes their fancy. Ethics is nice but sadly not everybody operates on the same rule set. There's even some "what do you mean you won't draw for free?" people. There's a couple of my artworks that found themselves on somebody' RP forums in user profiles. I could've raise huge stink about it and begin demanding that they tore it down and apologise and everything... But what's the point?
Uh, this is exactly my point about the commissions? you commision the artist to make a design for you, and just provide your input. You know, like they work in the industry with concept artists?
In my eye adoptable - in this specific situation, I don't talk about people who like collect them or specifically search for randomness - is akin to going instead to shutterstock and buying some clipart to serve as your design. It wasn't made for your project, so it won't fit in there seamlessly. Especially since I saw that quite a few adopts have licenses attached to them that explicitly forbid you from modifying the image or the concept in any way.
Yeah the problem is that I cannot not feel anything towards a bunch of pixels. That's why I watch films and become emotionally invested in stories and stuff.
Okay, how about "sell a piece of your own soul" then, instead? Any artwork is an act of self-expression, and therefore it cannot not have a piece of the author's very essence in it.
No? Nothing stops you from granting the, as the lawyerfolk say, "irrrevocable license" to use your ideas to your customers? Functionally it would be the exactly same thing, only that they wouldn't be able to claim that they come up with that idea since they have all rights to it.
I'm not. That's why I commissioned a few artist to make several concepts to me.
Again, I'll repeat myself, or clarify, I do not think that adopts are evil or wrong.
Adoptables seem big in the furry community where having a drawn avatar is very important, but not everyone is an artist! It isn't inherently a scam (there are commission scammers everywhere!) it seems like a pretty neat way to provide unique character designs to people who want or need avatars.
I've also seen them become pretty popular within the TTRPG community as well, for the same reasons!
I think the major problem is that you don't understand that its "Not that deep" as it seems to you.
Yes, of course an artist puts love/soul into a creation, but they always do, with every piece, even with commissions they draw of existing characters. That doesn't mean that selling the commission, or any art of that matter, would be somehow bad or robbing the artist of their soul.
I know for a fact that I dont have a personal connection to everything I design. The connection usually comes with the characters story and personality, if they dont have it, they're just a design I dont feel connected to, and had no problem selling to someone else who likes the design and might feel a connection to it. I'm sure other artists feel the same way, otherwise the adoptable market wouldn't be so oversaturated.
And to come to the point I mentioned again.
You can only commission an artist to manufacture a design for you if you already have an idea in mind of what you want. No everyone has that when looking for characters.
Sometimes yeah, you 100% know your character and what they're supposed to look like (mostly), then yeah, it makes more sense to commission an artist to bring your idea to life.
But if you're just casually looking for characters to own/use, without sth hyper specific in mind, adoptables are a great alternative.
And in the end, everyone is able to treat their intellectual property the way THEY want, if they want to sell a design now or not, and everyone can spend their hard earned money the way THEY want, and if they want to spend it on a 30$ adoptable they think looks cool I won't stop them.
I've seen my fair share of adopts in the other art community so these are mostly just inputs from an outsider; (I couldn't buy myself adopts because I prefer designing my own or I would most likely change the design, which I would tell on later on here as part of reasons why people buy adopts)
The community is oversaturated in a way (see closed species and whatnot). It's a large market, there is competition so some make-do with their prices hence why the gap looks big. Those that's usually priced high are because of high demands (+ auctions). Some buy them for sake of having a design of said designer and whatnot. Really, just look at closed species for an example hgfds
Now for the other point; Some use adopts as a base for another concept. Not all adopts are bought and kept as is, especially for a long time (so you see people rehoming them too if they really can't connect anymore as much). I myself have a few characters I got from others for free or in exchange for art that are mostly personal use and most of them I altered to fit my story/aesthetic better.
Customs are harder to come by because not everyone can visualize the design they want. Conceptualizing is one thing but execution is another. You may need to redo it over and over unless you really have a nice solid idea of what you want it to look like. Whereas in adopts, the design is already there. Maybe just a few tweaks. Plus they can get expensive than say something like the usual adopts (the community is more or less saturated).
Every designer/artist has a different TOS and I'm sure most of them would find no offense in being asked about clarifications or whatnot to which extent the characters can be used. That is to not say there are certainly other scams done with a suspicious ownership tos but for the most part, the character is yours and that's just it. It's a win-win for both parties, you get a nice character and the artist gets paid. 
Generally you're buying a few things
1 design
2 the "story" that the character will fit into
3 limitations in how you'll be able to use the character you've purchased
Limitations vary by artist and creator, but most of what I've read state generally that they need to stay restricted to the world type they were created for, ect. And of course, credit is always used, and there's a blurry line (sometimes addressed) on if the character would then have Rights to the Purchaser to use ie for covers of novels, in a comic, ect things that make money off of the "art design". And generally, the artist retains these Rights, unless you pay more to purchase those with your individual design.
I'm not "in" the community generally, since I haven't personally seen a use for it. But the few artists I've followed on dA ... pretty much all of them have a world restriction to them and I don't recall them stating that they're closed. Rather that in some cases, I recall it being "open" but that it's restricted to the sense of... The artist created a few for themself, and made more and more in this world, and their fans came to them wanting characters to interact in that world as a community... Kind of an interesting evolution in that people came to them to ask for the adoptables.
I've seen instances like that with fandom based design (i.e. Sonic, My Hero Academy, BNA, etc.) they usually/sometimes don't want the design rehashed or altered for something else as it was intended for that universe specifically
yeah it's roughly the same with what @nostalgicroxas explained about open/closed species so if there's adopts open for that species it's sometimes limited to the world the artist made those species for
