I cured a few villagers that raised their prices a bit, as well as villagers I hadn't cured that many times yet, then left the game. When I joined the world again, the villagers had lost their old discounts, and it was as if I had cured them for the first time, making me go through the process all over again.

I don't think any screenshots will make a difference, it just made it so the old memory of discounts went away.