Yes, I agree that it is not fair to do so. I really do... and we don't plan to do this very often - what is free today will be free forever! Except in cases like Monthly Expense and Monthly Income where we did not fully think through the life cycle of a feature. But even these, the Monthly Expenses and Monthly Income that free users have already created for Auto Entry will get auto entered, free users just can't create new ones for auto entry.
I'll explain why we decided to make these premium - we have several user accounts with the auto entry feature on that have been abandoned. These entries continue to be added even when no one is monitoring these accounts. So we said, let's have this feature only for users that are actively using (and paying for) expenseRegister.