The Price is (Not) Right: Comparing Privacy in Free and Paid Apps.

(…) there is no clear evidence that paying for an app will actually guarantee protection from extensive data collection in practice. Given that the free version had at least one third-party library or dangerous permission, respectively, we discovered that 45% of the paid versions reused all of the same third-party libraries as their free versions, and 74% of the paid versions had all of the dangerous permissions held by the free app.