To be honest, pricing your commissions is never easy. I'm a professional (in the making) if you want to call it like that, and I'm still torn between "what can my followers afford" and "how much is my art and time actually worth."
My prices are considered ridiculously low for a professional standart but again, my followers don't have enough money to justify higher prices atm. Anyway, you can have a look here.
In general, I'm always checking people around me to not end up with unaffordably high prices, but one of my profs in my first semester actually proposed another approach (which I always use as a base):
You need to know X amount of money you want/need to make (per month, in this example I'm generous with 2,000€, which is kind of a better low income per month here), Y amount of hours you are able/willing to work per month (remember free time, vacation days, other stuff, here I'll go with an ordinary 40h week -2 vacation days per month so I'm at ~160h per month), and with that you can get your wage per hour.
2,000€/160h=12.50€/h for a regular 9 to 5 job
You can alter this with how much money you would need to make per week, for this example 500€, and so on, depending on what works better for you. I think calculating your personal minimum wage is more reasonable than looking at your government or the international comparison because it doesn't always work out. It also lets you adjust your personal paycheck raise, for example when I'm done with my studies I can demand at least twice as much with the same work hours. (Plus all the taxes and whatnot I'd need to pay by myself then.)
Again, this is just you personal minimum wage per hour and not per commission, and only what you can earn ideally because you still need to get customers first.
Another thing to consider: you also have work hours you don't actually spend on drawing the commission but just being in contact with your client, talking about what they want yadda yadda, and maybe doing some research. All of this also need to be reflected in your commission price, after all you're providing a service in first place, not just a physical product. It's a bit different if you just draw whatever and later sell the illustration to a customer.
Also make sure to show a consistent quality in your portfolio, and make sure your art generally keeps up with this standart. Clients need to know what they are actually getting, otherwise it's not really worth an investment for them. If you consider yourself not skilled enough at the moment for a specific style etc. then don't offer it. Only offer what you can get done in a reasonable amount of time. If you're uncertain about your personal wage, look around at artists with your skill level and what type of commission they (successfully) offer.
In general, pencil sketches will not earn you as much money as an illustration with clear lineart, colour, and background. A bust will cost less than a full-body drawing. 3 characters are more expensive than 1. So stacking your commission prices is really helpful to get a feel for it imo and gives clients a chance to choose a type that is closer to their personal budget.
Hope this helps!