Changing your Username in Roblox will cost you 1,000 Robux, equivalent to $14.98. Whereas, the display name feature debuted in 2021 which is different than changing your username.

A Display Name is how other players will see you in-game. This feature appeared in 2021 and is available to all players free of charge. While Usernames are unique, two or more players can have the ...

The process for changing your display name on Roblox is fairly simple. Here's a full breakdown of how you can change your display name in Roblox.