Let’s assume you have a mobile game and thinking about great ways to start a earning from it. On the other hand, if you don’t own one, you will probably have one in near future if you run an iPhone or Android app development company in USA.
A game usually can earn by three ways, first - a certain downloading fee, second - in-app purchases, and #3 - monetization through ads. What you charge for your mobile game or- how do you set in-app purchases depends on the concept, quality, type of the game, and ultimately your consideration.