Well, you can't give the user a taste of what the full feature set is like when you have an inapp purchase. What dev want is a way to have a full featured app

Well, you can't give the user a taste of what the full feature set is like when you have an inapp purchase. What dev want is a way to have a full featured app that expires after a certain amount of time, not a limited version that enables all features over a paywall.