One pain is sandboxing makes it difficult to migrate data from v1 to v2. You need to build an elaborately kludgey data export/import feature by hand, in both ve

One pain is sandboxing makes it difficult to migrate data from v1 to v2. You need to build an elaborately kludgey data export/import feature by hand, in both versions. More importantly, how do you charge upgrade pricing? Any user who encounters 2.0 on the store is charged the same price, whether they own 1.0 or not. There is no easy way to give 1.0 owners a discounted price. There are elaborate kludges to work around these limitations with a great deal of work. Apple could make producing upgrade versions easy, like they’ve done with subscriptions, so devs can focus on improving their product value instead of purchasing mechanisms.