Incredibly informative and thorough piece by MacStores on the top grossing iOS apps. Some takeaways that you might have assumed:
1. Free apps rule all
2. Given top apps are free, they monetize through in-app purchases
3. Top apps typically have 10+ in-app purchase opportunities that are <$9.99
4. Games rule all
5. Top app shops include King, EA, Big Fish, Zynga, SGN. All games.