Some Enchanted Items Say "Too Expensive!" on Anvil Even When You Aren't Repairing Them.

On my world, I was checking for enchantment levels when I noticed that for some reason, when only my pickaxe and trident were in one slot and nothing else was in the other one, it said "Too Expensive!". I hope that this isn't a feature and that this is just a bug.

Steps:
1: Get and item
2: Add some enchantments to it
3: Get in survival mode
4: Try to enchant it again
5: It says, "Too Expensive!" before putting anything in the second slot .

Expected Results:
You would be able to enchant it with enough exp.

Observed Results:
It says, "Too Expensive!" even when nothing is in the second slot making it impossible to enchant/repair