In 1.21.4 the 'too expensive' limit is not removed (in survival, singleplayer, option set in the config).

Hm... seems to work fine for me? (On Fabric that is)

Though I did get a crash when trying to save the config (ActionResult was changed), gonna check what else broke.

1.21.2 had a binary compatibility change with ActionResult (in other words, mod needed a recompile, no code changes though).
Other than that, I can't find any other issue in 1.21.3 or 1.21.4 either, so I'm not sure why it doesn't work for you.
Tested NeoForge too, seems to work fine.

Since saving the config crashes the game, I assume you haven't touched the config at all, right?
Did you join a multiplayer server prior to going singleplayer?
The mod has some complicated config sync logic to ensure(?) that client and server use the same config and it's supposed to use the local config in singleplayer, but maybe something failed in that logic.
If you only went singleplayer and haven't touched the config at all, I can't imagine the config sync being the issue, since the default is to remove the anvil limit and both server and local config would be set to that.

Can you try restarting the game and see if that magically fixes the issue?

If not, the only other way I can imagine it failing is due to a mod conflict / mixin error.

Can you post your latest.log?

Problem solved, issue was in the chair.

Config didn't crash for me.

I just retried with a fresh Prism instance and still have the same behavior with the version you published a couple of days ago, and no other mods beside the deps for this mod.

logs found there https://mclo.gs/cD2M8yJ

Problem solved, issue was in the chair.

Haha, now I wonder what you did, but I'm glad it worked out in the end! 😄