It's a brutal world at the top of the iOS games chart. Very brutal in fact; if you can't crack the top 100, you're not going to make any kind of appreciable income.
Gamesindustry.biz reports on a study undertaken by Newzoo that looked into iOS revenues for the top 1,000 games for the iOS platform.
The good news is that if you can crack the top twenty, you're going to be rolling in dough, with games in that bracket earning a combined global average of around $US13 million. The bad news is that revenues trail off rather alarmingly after that, with games in the top 50 barely cracking $US3 million in revenue, and games in the 50-100 bracket not even cracking a single million.
End up outside the top 100, and the average revenues sat in the simple thousands of dollars, which might work for you if you're a one-person development team, but is unlikely to pay the bills if you've got staff to pay.
iOS game revenues show top 20 dominate - Newzoo [GamesIndustry.biz]