How much money does the average person make from a iPhone app?

I want to make an iPhone app and I have a good idea and I want to develop it and then put it on the App Store. How much money is usually made? Say per month? I know it's a rather general question but thanks!

Just about $1.79 before taxes.

I made $12, 000 per month the first 5 months.
now its like $1100-3000 per month