When you are curing your villagers for the discounts and you log out of world when the villager is in zombie form or getting cured, the villager will change his prices such that the last one or more curing will not count. 
Eg: I am curing clerics to trade rotten flesh with. I curing the same villager 3 times bringing prices down to 11-14(I don't remember exactly). But, I logged out of the world after turning him into a zombie villager. Then when I log back in and cure it, the prices are 26 rotten flesh for, more then what were before I logged out. I locked his profession after first curing as well