Gartner also predicts growth in free apps compared to overall downloads. This year, those apps requiring no cost to download will make up 91% of all app installations, rising to 94.5% by 2017. And the metrics firm believes that in-app purchases will grow faster than premium apps according to Gartner. Paid apps (aka premium apps) will grow at an annual compound growth rate of 14.22% from 2012-2017. Meanwhile, during the same time period, in-app purchases should grow at a compounded annual growth rate of 27.83%.
That means that the money charged by game developers for things like extra lives or special weapons, will account for 48% of mobile app store revenue by 2017, up from the 11% it represented last year. In-app purchases happen to represent a large chunk of the revenue racked up by the Apple App Store, more so than for other platforms. Eventually, Gartner sees the other platforms come close to catching up to Apple in this regard.
source: Gartner via Forbes