Great plugin. It should have appeared immediately after 1.14 was released. Sometimes deals become very imbalanced, especially due to repeated cures of villagers or simply significant discounts. We all know the sad joke about buying bookshelves, breaking them and then selling books back for more.
This is nonsense, which the developers themselves have not yet corrected. This plugin will allow you to fix some of the distortions that have arisen with the villagers trade in the latest versions. For additional modification of deals, I recommend (I don't know if these plugins will work together) -
https://www.spigotmc.org/resources/custom-villager-modifications.78329/