EXP upgrades to R inventory are still processed as e500 "sticker" upgrades, just EXPs have an unlimited (free) supply of them. The method of upgrading is the same as those who must earn/ purchase/ redeem stickers. Also, many EXPs do keep some stickers in the account btw for companions, who can upgrade at the EXP window, but whose status nonetheless requires an actual e500 redemption.