Whenever you talk about making money on free games, you have to talk about Ngmoco -- that company famously choose "freemium" as its business plan, and business appears to be good. Exec Simon Jeffery confirmed exactly that at a conference earlier this week -- while he can't discuss actual revenue, he says things are going well. And of course other companies who already know how to make money from free games (like Zynga, whose Farmville recently released on the iPhone) will see this as a big green light for joining Apple's platform.
The revenue per user isn't the only important stat here -- Apple also has plenty of users to offer up. Disney's free Toy Story 3 app released recently, and has already picked up 1.7 million users, a good number of which probably bought the 99 cent in-app game offered up. Lots and lots of users spending a surprising amount of money inside their apps means lots and lots of revenue for both iPhone developers and Apple.