I think Amazon's pricing example is based on a fairly unrealistic use case where you only sync at the end of a session. With real world applications, most of th

I think Amazon's pricing example is based on a fairly unrealistic use case where you only sync at the end of a session. With real world applications, most of them sync multiple times during a session, e.g., every 5 minutes, every 30 minutes, every time a significant atom of work is done (e.g., Gmail saving drafts). With mobile devices it's common to turn them off abruptly, or lose connectivity abruptly. A user's not going to enjoy the experience if nothing they did in their session on their phone is available when they fire up their laptop because the phone app only syncs at the end of a session.