Professional comic artists do about one page per day. So, whatever a full day's pay for you is. Adjust for your actual production rate and hassle factor from the client. At ten bucks per hour, that's about eighty bucks for labor, say twenty bucks for materials and you have a nice round one hundred dollars per page.

They would be digital so it's not much for materials, it's time. Time is the biggest factor. It takes me AT LEAST 1 to 2 hours to draw the lineart, 8 hours to color. I think $100 per page would scare off customers (I would ask that from a company but not an individual). But I don't want to go too low either because of how labor intensive comics are.

It might scare them. But, you still gotta put a roof over your head and feed you doggy, so don't undervalue yourself either.

I know I got a comic commission from  amonomega a while back. I checked my notes, and he only charged $45 for color and $35 for inks. I went with the $35 option, and although I had to remind him about it later, he still delivered, as well as giving me a free avatar commission to make up for his forgetfulness. I'm still using it now, though I may contact him or someone else to get a different one made.

Of course, part of the reason he gave me such a great deal is because of how well-written and simple my idea was. Plus, it was only a one-page comic. Try to keep that in mind. If the commissioner has a good idea for what they want already, you can offer a discount depending on how much easier they've made your job (though you may wish to keep that private so people don't start demanding it). You should also consider how many pages the comic will require, and charge accordingly. I personally think anything from $30 to $50 per page, depending on complexity, time, and how much work the commissioner leaves to you, would be quite reasonable. Some might disagree, but then some people are unreasonable by default. =P

In any case, try to keep some simple economics in mind: When the price goes up, demand tends to drop off and you'll have fewer customers. When the price goes down, demand tends to go up and you'll have more customers. There may be other factors involved, but this is the general rule. Try to find a price you're comfortable with, then adjust it up and down depending on how much work you want to take on, and how much income you wish to pull in.

Also, I would suggest charging more for "erotic" pieces, whether they're comics or just normal pictures. Demand is usually always high for such art, and it can discourage people from using you as a porn vending machine. And always reserve the right to turn down a commission if you don't like it. It's your art; you should get the final say, within reason.

30 is too low for me for color. I charge that for a single character, fully colored and shaded, no background. 45 or 50 sounds about right for full color...

This person is looking for a whole story, but I may turn that down, though I'm willing to do a few pages. I wouldn;t accept comic commissions at all from random strangers because of how much work goes into them... but this is from someone I've been talking to online on and off for over a year.

Also, I don't draw porn! Somewhat erotic art, but never been commissioned for that because I don't offer it as a commission. Since it would be a story, I'd be willing to draw characters either going to bed or waking up in bed together, but nothing explicit. I don't think this person wants porn anyway, they are looking for a more mainstream sci-fi/ superhero/spy/action type comic based on their original stories.

That's fine. I was just trying to cover as many of the bases as I could. Sounds like you've got some of the details nailed down already. Good luck on the comic! Hope it's everything they want!