It's a feature of the game. It has been since anvils came out. Things have a limit of 39 levels in the anvil.
Right now, you can rename it, and it's under that limit. However, the levels needed to repair it increases each time you repair them, eventually becoming too expensive, like this. Basically, you've replied them them.
While you probably won't be able to get these ones ever repaired, there are some ways to avoid this on your next pair:
- Name them first. This sets the maximum repair limit at the current one. Or something just above it. Really helps
- Put mending on them. Then they'll repair whenever you get levels. Kinda nice
