I'd be interested, but this is very vague!
Have you bought software before? Do you have a contract in place to protect both yourself and your client?
Assuming the answer is yes, a few more questions(!)
Your spec leaves a lot to the imagination; you mention map select and upgrades: Who's planning them? The programmer? Or is there a brief in place that has to be followed? This can definitely change the price!
Next up is leaderboards, what do you mean by that? A local high score table? Facebook leaderboards? GameCenter? Do you have a server if you're going for web-based leaderboards?
The final thing I need to know is what platform? You mention mobile but that could be anything from iPad to a HTC Desire HD. Will you be handling the porting for each device or do you want it to be optimised?
I've haven't charged a client for C2 work before, but based on previous jobs $500 would be the starting price, as well as a solid design document and contract.
Hope you find what you're after <img src="smileys/smiley1.gif" border="0" align="middle" />