Anecdotally, developers consistently tell us that they make more
money on iOS, about three to four times as much. To be sure, we
pulled a sample of in-app purchase data from a set of top apps
with versions on both iOS and Android, comprising several
million daily active users (DAUs). Running the numbers, we find
that, on average, for every $1.00 generated on iOS, the same app
will generate $0.24 on Android.
The facts have a pro-Apple bias.