iOS Games: Design Principles for Monetizing Goods
To successfully monetize your iOS game, you’ll want to frequently display the virtual goods your players can buy and give them plenty of opportunities to buy them. Offer regular, limited-time discounts or sales on special items to help get your players in the habit of checking for deals. To prevent complaints and encourage continual play, make sure that some of your free in-game items are better than the ones players can buy with in-app purchases. Consider selling virtual currency instead of virtual goods; then, you can adjust item prices as needed and avoid the app approval process that comes from adding new items.
See Chapter 12, “iOS Game Design: Basic Principles for Growth and Revenue,” for more information.