Distimo has released an interesting publication which looks at the Apple iTunes App Store – even though that is not, by far, the only app store in existance, it is the one which started the App Store Phenomenon.
Sadly, it is also the one which declared the extincion of the paid app. The chart below shows the falling percentage of classic paid apps over the years:
In addition to that, the following data could also be useful:
Find out more in the PDF…