^^^^^^^^^^ THIS.
Also, yeah, hourly wage is my starting point, too -- when I was working at Target, I got paid 8-something an hour. So I figured, if someone commissions me for anything, I gotta figure out how long it takes me to do that kind of thing. If the sort of page they want usually takes me 5 hours, then I gotta be making more than $45 an hour on this commission, or else I'd be better off declining the commission, taking extra hours at Target, and just drawing the things I want to draw.
And given that my art requires a lot more skill than working at Target, I would base my pricing off of: I shouldn't work for less than $10 an hour. That's still kinda cheap, but it made it easier for me to decline jobs that really don't pay enough without feeling greedy, because I knew that number wasn't arbitrary.
I don't think it's a problem trying to be fair to both of you --- it's a problem if you're unfair to yourself out of insecurity that you might be perceived as unfair for asking a reasonable price. If you figure out what you need, and they think it's a lot, it's still being fair to both of you to ask that price!
Though I will say, while I don't feel you should sell yourself short -- there's something to be said for non-financial benefits. The first comic I did was a script by a peer/friend with a lot more experience in writing and drawing and publishing comics than I had, and I took it even though she wasn't able to pay very well at that point -- because I knew she was good at her job and could teach me a lot, and the project was pretty short. Learning from her was worth it to me. If you say "I'm asking $80 a page" and they say "shoot, all I can pay is $50" -- it's up to you to decide whether that's worth it to you.
