Anvil Cost Calculation Incorrect

The Cost of repairing a Diamond Pick Axe with Unbreaking III, Silktouch I, and Efficiency IV was too expensive with 37 levels available. However a Diamond Pick Axe with Unbreaking III, Efficiency V, and Silktouch I only cost 1 level and a couple of diamonds to repair. Even though this time had more enchantments... level V efficiency vs Level III.