My question for point #2 is in the line of the need to perform data migration actually.
Let's say you have a bug on your code in a way that the data stored currently are wrong and you need to fix them up by performing a batch update. Would that hurt you in terms of cost? How would you handle such situation?
Or let's just say that your user profile data model needs to be re-jiggered to support a new feature (adding columns, changing current columns, etc).