Windows Phone 7 (WP7) Marketplace could potentially make developers a lot more money than it currently does if it moves away from paid apps with free trials and introduces in-app purchasing.

Around 80 percent of the 20,000 paid downloads from the top 300 apps in the US in October were free trials for paid apps, according to apps analytics firm Distimo, meaning just 4,000 downloads per day actually generated revenue. With the addition of free apps, a total of 121,000 app downloads took place each day, of which the paid apps making revenue accounted for just 3.3 percent.

Monetisation opportunities are also being missed due to the lack of a widespread in-app purchasing platform for Windows Phone apps, with traditional one-off fees currently the only monetisation method for paid apps in WP7 Marketplace. However, Distimo said the fact that the recent Microsoft ‘Beard and Beaks’ game features in-app purchasing suggests in-app purchasing could come to more Windows Phone apps in the near future. More than half (54 percent) of paid apps on WP7 Marketplace are games.

Paid apps have been added to WP7 Marketplace at a fairly constant rate of 1,300 per month during its lifespan, while the rate of free apps added has hit 1,650 per month.  At its launch in November 2010, 70 percent of apps were paid. By June 2011 free apps exceeded paid apps before Microsoft culled 1,000 free apps as it looked to restrict developers to publishing no more than 20 apps with similar functionality each day. By October, the number of free apps once again significantly exceeded paid apps.