Apple is betting that the allure of being tied into their incredibly efficient iTunes payment ecosystem (along with its 100 million + accounts tied to credit cards) will outweigh the downside of having to pay them a 30 percent fee. The same 30 percent fee they currently take from the thousands of app developers collectively making billions of dollars off of the App Store. And the same 30 percent fee they currently take for all other types of in-app purchases.
It’s hard to ignore iOS if you’re a publisher wanting to push into the mobile scene. I think most will end up buying into Apple’s system simply because they are out of options.