Halfbrick has noted massive growth for Jetpack Joyride since making the iOS game free late last year.

Marketing officer Phil Larsen told Joystiq at DICE that the game made about 1 million sales as a $1 purchase, but has been downloaded 13 million times as a free app.

Halfbrick estimates 5-10% of free users spend at least $1 on the game, and said revnue has been "higher" than before the free-to-play conversion.

A major update for Jetpack Joyride is expected soon.

The Australian developer also revealed that its slice-and-dice fest Fruit Ninja has shifted 500,000 units on Kinect, and that there are plans to continue updating the iOS version.

Thanks, Shack.