I have take 3 zombie villager, cure it, and set there profession to butcher.

after 3-4 cycles of trading/looking trade, for 2 of the villager, the number of items ask form an emerauld was more then the default trade. The trade affectected: (coal with 1villager/3; sweet berry 2/3; steak 2/3; kelp block 1/3)