Users should be able to revert their username (at least within a certain amount of time) free of charge, let’s say someone changes their username but dislikes it or wants to save it for later and desires to revert back to their previous one. They would have to pay another 1000 robux on top of the other username they’ve changed to.
It would be a lot more convenient to let users select the old username free of charge whilst also keeping the new one as they’ve already paid for it. Additionally, the user practically owns the previous username and any other previous username considering Roblox does not wipe old usernames from being reused.
However, to reduce demand, users should only eligible within a certain timeframe from the date they changed their username to revert. It could be a sort of last minute change.