Well... this is a tough question, you'll need to think mostly about your local currency, the economy of where you live and then, just then other aspects as skill, prestige and time it takes you.
For example and this is going to scare the crap out of anyone. But the minimum wage in my country is around $340 USD a month, devaluation and a dumpster fire of an economy if you ask me but that allows me to either
A. Take advantage whenever I go for international prices as if I were from a First World country
B. Offer discounts for friends, colleages or simply give them any cheap price, enough to not make them feel guilty but enough so they won't suspect I'm charging them way less lol (I also offer them types of commissions I literally have not listed on my PriceList, God bless them they never find out hahaha)
For example... I have two different arrangements with the series I draw for... 20 panels for one is $40USD (But I have all the freedom I want, Writer doesn't even asks me for corrections or anything) and for another one, despite the process is the same is $60USD (For this one, we do corrections and treat it more like a commission) but of course that's what I agree with each contractor. There was another person who paid $7USD per panel but for this one I was specifically asked to do it in a grayscale pencil sketch-like aesthetic.
The thing is, yeah I charge way less than what should be expected, and mostly because the story does in fact interest me. But at the same time I have a very steady income of commissions that compensate entirely for what I earn in a month and regardless of the type of commission if I feel like it I can finish more than one within a day (For as long the client gives me clear information and instructions, and is quick to respond whenever I have doubts or provide updates or leave the commission totally to me)
I'm also hired to make exclusive content for two Writers's Patreon so that's that as well...
So first would be important to measure your expenses, how much you need to live, how much you need for your services, extra cash in case you want to spoil yourself or have health issues.
I know certain countries are stupidly expensive when it comes to this, on my end... most of health care is quite free or not that expensive, to put an example... an ingrown toenail removal costs here around $12 USD but in USA, treatment costs around $120 - $375 (Based on a quick Google search)