The ability to have a discount if a user has purchased another Upgrade - would be brilliant. Reason is that I'm adding Upgrade2, which includes all the features of Upgrade1 - but a few more. I suggested here to have it so normal users require Upgrade1 to purchase Upgrade2 but it didn't receive any attention. Currently, my users feel that their purchase of Upgrade1 was a waste - and that isn't how I want it to be. I want to discount Upgrade2 by the price of Upgrade1.