I draw comics about my life :D

Just give the customer a few examples, it can't be that hard to show them some of your work and say what they cost.

With art you can always say "It depends on what you want" ie. Level of Intricacy and detail etc. "Send me the details of what you want and we can look at pricing from there."

No she's waiting to see just how much value he puts in handcrafted art