Update: MKStoreKit 3.0, an updated version of the one presented here is available. Please check it out and use 3.0 instead of this. In-App purchases is a great way for developers to upsell by giving away their app for free and then allow them to charge for features when users start using it. This freemium model has indeed worked very well for upselling your app in the AppStore. But unfortunately, there isn’t an Apple allowed way to...