A new report from the NPD group has found a significant proportion of what it calls "app gamers" have splashed out on in-app purchases.
The figure includes both virtual good and upgrades from free to paid versions, with an average transaction of $3.
The NPD's Liam Callahan said app gamers are used to playing for free, making it tricky to get them to spend; he said developers must find a pricing "sweet spot" to be successful.
“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%," he said.
Those who use smartphones are less likely to spend than those who play on tablets, and 23% of app gamers exclusively play only on mobile devices - not on consoles or PC.
This last fact is particularly irksome as app gamers don't spend as much as their core gaming cousins.
"Another opportunity for the industry as a whole is to convert mobile-only gamers to engage in other gaming activities across portables, consoles and PC’s where we see more money being spent per user," Callahan noted.