Repairing renamed object too expensive prior work penalty too high?

I have an iron pick that has only one enchantment (unbreaking III) it was renamed back while we still played 1.7.4 version. I had no problems repairing it since we started playing with the snapshots, until yesterday when I wanted to repair it, as soon as it was put on the anvil it said "too expensive" which from my understanding shouldn't be the case with a renamed tool.