The cost of combining two items with the same enchant at different levels is based on the increase in level, not the final level

If two items share an enchant but have different levels and they are combined in the anvil, the cost will be incorrect.

Steps to reproduce

1. In the first anvil slot, put a sharpness I book
2. In the second slot, put a sharpness V book

Expected results

The cost to combine the items is 5 levels

Observed results

The cost of to combine the items is 4 levels