What about free + admob? Angry Birds is free on Android, but uses Ads to support it. Being the top free game on the platform, this means they probably do a lot of money with it.
Rovio specifically said that they went Ad-supported on Android because NONE of the top apps were paid, and they didn't think they'd make much money with a paid app. There was a lot of talk about make a paid version without ads, but it never appeared.
Yes, But why is it so? Angry Birds first became very popular on iPhone and then was ported to Android. It could be that if they started on Android the outcome could have been different.