Villager trading discount bug

After trading with a villager for a while, I got the usual slight discount for most items. However, the iron ingots trade was marked up from 4 ingots for 1 emerald to 7 and then 9 ingots for 1 emerald. This was not just a cosmetic bug or typo on the GUI, and was the actual trade price. The rest of the discounted trades were discounted normally as expected.