Around 30% of app gamers have made either an in-app game purchase or upgraded from a free app to a paid version, according to new research from NPD.

The analyst’s Mobile Gaming 2012 also reveals that $3 is the sweet spot where app gamers feel they have received a good value for an app game purchase or a free-to-paid app upgrade.

“Many mobile gaming consumers have grown accustomed to gaming for free, making it essential to find the sweet spot for pricing that encourages purchasing by as many consumers as possible,” said Liam Callahan, industry analyst and The NPD Group.

“Mobile game developers and publishers need to be able to maximize their opportunities by identifying ways to increase the number of gamers willing to upgrade their free apps or pay for in-app purchases, which currently stand at close to 30%.”

Finally, the reports reveals that 23% of app gamers – defined as mobile gamers who play most often on a smartphone or tablet – only play on mobile devices.