The RP use to upgrade instead of buying them outright, might be better, but I would double check to make sure that you aren't using more RP to get the earrings you want than you need too. I however have the NT earrings from the vending machine and don't plan on using them again. Would be nice if I could sell them to the vending machine for a good amount of gold(1k would be nice) as I don't suspect they'll every make a level 74 earring that would require me to upgrade the earrings from 54 to 74. For now they'll just sit in my warehouse.