Economics

I'm starting to ponder, well, the economics of this all. As my background, I should explain that I was a math/biology major in college, who never took a business class, and though I understand little of the field, my mom was an accountant (and I think at least a little has rubbed off).

I'm trying to figure out, if my goal is to at least break even, what costs I have, and how much I can charge. I mean, at least the theory in accounting is you take (up front cost + desired profit)/(expected sales) = (profit per unit), I think anyways. However, what gets me is this: what are the expected sales, how will each cost (mainly artwork) affect sales, and how will price affect sales? I mean, as I've said, if I can sell only 1 of my games for $500, then I'll be in the black, but that probably won't happen.

I guess what I need to ask for each cost is "Will it pay for itself, or is it needed?" I mean, if I spend $100 on artwork, will that generate at least 13 extra sales? What if I buy a cover art piece, will that generate the 15 sales to cover it's cost? What if I doubled my art budget, would I realistically be able to sell 60 copies? And if my art budget doubled, would I be able to sell my game for $17 or $20 instead of $15?

I've posted to The Forge about this, and am waiting for a response. Most of the previous things I've read have been very qualitative (things like, "You need to make a strong visual statement") but little in terms of actual numbers. I mean, maybe I'm expecting the economics of indie RPGs to be a science (the way economics kind of is), when it's not. Or, maybe I just didn't see the right posts, and actually all of my questions have been answered already but are hidden from me.

Simon