Free apps utilize a variety of different sources of income to contribute to the resources they use for the creation of their apps. Mobile apps can potentially make lots of money, even billions of dollars. The top 200 apps on Apple’s app store make $82,000 a day! Of course, gaming makes more than entertainment apps.
The biggest primary sources of income are advertisements, as well as in-app purchases. A good example of this is Clash of Clans, which was one of the most popular free games on mobiles, and they made most of their money through the purchase of Gems which ranged from 99 cents to 50 dollars.