How much money can be made from a somewhat successful mobile app?

I'm considering either iOS or android, and either making it nonfree or free (but with ads). Suppose it got around 100,000 downloads and the pay version is priced at a dollar. How much can a developer make in all of the 4 scenarios?

I'm completely unfamiliar with the policies in either market (for example, how big of a chunk apple takes or how ads work). What are other things I need to consider?