Basically in-app billing lets users pay for trials, virtual goods, upgrades or other kinds of commerce while still using an app, according to Eric Chu on the Android Developers Blog. Google also takes a 30 percent cut from the purchase -- in-app or outside, the same as the Android Market.
The cut pays off Google for costs as well as distribution, Google spokesman Randall Sarafa told Press:Here.
Titles such as Tap Tap Revenge by Disney Mobile, Comics by ComiXology and Dungeon Defenders: FW Deluxe by Trendy Entertainment are already using the new in-app billing tool. It also gives developers a few news way to make money aside from monetized ads and Android handling the receipts.