I charge $75 an hour for graphic design, but I do logos as a package deal (includes 4-6 initial designs, a few revisions, and layouts for business cards and stuff) for anywhere between $750 and $1500. I'm fast, been doing design for 25 years. When I lived and worked in a big city, those numbers were easily doubled.
Since this is your first go around, you can't really charge the same amount as someone with more experience. You may well have challenges that you'll need to deal with (creating print ready files, figuring out the client, etc.), which can also add time. You have to decide how much you want the job, and if it's worth not making very much. Make sure your client understands this is something relatively new for you, and as such you'll charge them accordingly. I'd suggest a couple hundred bucks. That's VERY affordable, and you shouldn't try to sustain it. As you get more work, your price goes up.
What you're getting paid for the illustrations is $1.37 per hour. Unless you're independently wealthy or are just doing the work as a hobby or a favor for a friend, you really need to value your services more. You have real illustration talent, real talent at a high level that's hard to come by. That has a lot of value!
