Well, the prices look pretty decent for me, very average and proper for someone that hasn't been doing commissions in a long time or is stepping on that field for the first time.
You are not ""underpricing"" yourself, it is a very reasonable price for someone that is likely not from Latam, Vietnam or Philippines, who tend to go from $25 and under if they are not popular or just started to promote themselves internationally.
I hope you're also keeping in mind is the fee for transaction / payment of the platform you're using.
For example, I use Paypal, and it takes 4,5% in fees whenever I receive a payment. For example, one of my items is $40, client sends the money, then what I actually receive is $38.20. So yeah, it is important you are keeping that in mind for when you set your prices depending on what you're using, besides other pricing techniques such as working hours or similar.
Avoid listneinig to the people that says those commissions are too cheap, if they think so, then they'll commission you, if they think you're underpricing then they'll send you a tip. If the one telling you is another artist, be careful, since some of them have this friendly act of encouraging others to raise prices so they remain the cheaper better option. Besides, if you with this prices struggle to get clients, then its likely you're going to struggle more if you raised the prices.
Consider it like this: You manage to get 3 people commissioning you once a month, that means even if art is a luxury and not a need, they can invest that bit on a treat, but if the price raises then it won't be accessible for all of those 3 people and if your public is still small, then it'll take more time to gain the trust of newcomers by sharing commission works less frequently.
I've also made other observations, so pardon the intrusion:
There doesn't seem to be much of a difference in athe PFP and the Half-Body due to the proportions, try to make it more notorious so people can feel the importance of each service. I won't recommend removing the Half-Body tier since its a good psychological tactic to either guarantee you'll be commissioned at least the cheaper option, or clients will be more inclined to actually go for the expensive one.
Be careful about the amount of text in your commission sheet, while it is nicely arranged for viewing in pc, if I look at it from my phone then I would require to zoom in or open it up apart. So avoid having others taking an extra step to build interest for you, even if it's mundane, but those thing do influence your presentation.
The samples are neat, still due to the previously mentioned issue they might not be well appreciated on mobile, which sadly is in what people see the most nowadays, except probably for those that still use the Forum. I believe you're ok with your first image and while promoting yourself you could link to the expanded version with all ToS, Add-Ons, TaT, Paymenth method and other offers and more there. Be it in the post or leaving that info to copypaste whenever a client asks for more information.
For example, here I have my Pricelist besides yours with the biggest preview in my file folder. (Ignore the file name, it was mostly to have them side by side without editing)

My personal idea of the arrangement would be:
- One single image for the PFP and a more vertical friendly sample for the halfbody, the fullbody is perfect as it is.
- I would remove the "DM me" and just leave the payment method.
- Crop away the Do's and Don'ts and make bigger the prices, they are a bit harder to read on mobile and while th color choice is ok, it kind of blurrs viewed from afar or shrunk for data saving.
This one is important to avoid people going through all the process of the commission and last second after raising your hopes just to say "Ohh.... I can't pay through that", it's also a way to avoid scammers who try to get your bank account or force you to enter other platforms to """pay you""". Besides, nowadays even if its written on the post or the image, if you ask for DMs its highly likely you may end up receiving scam messages than actual clients.
I would personally recommend using a security wall, be it processing orders through Ko-Fi, Google Form, or others, that would require the client to them send your information instead of the other way around. Since you don't make NSFW or at least nothing Obscene, you can always encourage people to ask you questions in the comments if they have any doubts, that also raises the trust in the Artists and others can see you solve doubts and such.