applecrisp, it truly great, until it's all for free, you know. But more and more iOS applications start implementing payment system and in-app purchase tools, giving an option to the users to pay for any item or service in their app. You can take a look at ios payment sdk tools from a well-kniown dev company, which provides applications with such in-app payment-related services, if you're still don't know what I'm talking about.