I have an ongoing experiment. We have a game called WordRoom that is supported on four platforms. Three of those are free (with ads) and one is $1 for a download. The platform we charge for is iOS.
My thesis is:
"By paying for a game, you are less likely to uninstall it since you've created a fictional value. By uninstalling the game you'll feel that you've thrown you money away and/or admit a bad decision".
My data is not statistically secure yet but it points towards that our iOS users have the highest return rate of all platforms.
The experiment goes on...
The other platsforms are Windows 8, Windows Phone and Android.