So I recently created a villager farm to make some trades. I infected and cured some of my villagers several times to reduce trade costs; however, after trading with them a few times I noticed that their trade costs actually went up. Sometimes they even increased past their initial price (Ex. I had a villager that started off giving me 1 emerald for 4 books. I cured him thrice and got it down to 1 emerald for 1 book. It then suddenly increased to 8.) I tried curing them again, but that didn't change anything. I've never hit them.