This week marked an important moment in the evolution of the iOS app market. As Pages just slipped out of the iPad top 10 highest grossing apps chart, there are now no paid apps among the ten applications that generate most revenue on the iPad. When the iPad application market was born a few years ago, it was dominated by relatively stiffly priced applications, mimicking the PC software or game console software markets. But over the past couple of years, app vendors have realized that free apps with clever in-app purchasing hooks create much more revenue than paid apps.

The same applies to the iPhone — there is only one paid app among the twenty highest grossing iPhone apps today. It is notable that some of the highest grossing apps have relatively low download volumes. Clash of Clans has been the top-grossing iPad application for all of January, but it is only ranked 53rd on the iPad download chart. Hay Day is the seventh-biggest application when it comes to revenue generation on the iPhone, but is only ranked at #104 when it comes to download volume.

Leading app developers have figured out how to decouple download volume from revenue generation by creating free games that seduce their fans into paying steadily for in-app features. The types of of games that require a $0.99 or a $2.99 fee per download are turning into something resembling nostalgia items. For a stark example of how badly the revenue generation power of paid apps has faded, consider that the current #1 paid app on iPhone, Wood Camera, is 46th on the iPhone chart that lists top-grossing apps. The future belongs to free apps.