What to charge for a mobile app?

Hi everyone,

I need to write a mobile app and am not sure what to charge for it. I know most people charge by the hour but I want to give a flat rate because it may take longer and it's a learning curve for me anyways. It's basically a program that the user will login and view their account information and signup for available classes. The information is currently on a ms sql server and I plan to call some aspx pages to post and retrieve data. Doing this in spare time from my regular job and a weekend I can have it done in a week. Is $2000 too much to ask? Or maybe $2500? I know it's hard to judge without knowing the specs but I just mean from the client's point of view if that seems fair?

Thanks!