These apps are using the "freemium" model in which the software is available for free from the App Store, but certain features require the user to make an in-app purchase. This allows a decent experience for those testing out a title from the App Store while rewarding those who want to delve further into a game or the features of an app.
The study also breaks out the figures for Canadian Apple iPhone app developers and those numbers are about 5-6 times smaller. The average iPhone developer in Canada makes $11,558,18 from in-app purchases in the first month. Taking games out of the equation leaves an average of $4,226.71 in payments made to such Canadian developers.
IT looks like the study has given us a couple of facts. One, when it comes to the Apple iPhone, in-app purchases seem to be far more lucrative in gaming apps than for other genres, and it pays more to be a Stateside developer than one writing code in Canada.
source: Velositor via MobileSyrup