Cured villagers sell bookshelves for 1 emerald and buy books for 1 emerald, allowing players to easily get an unimited amount of emeralds

When trading with a Librarian villager, the trade that can available might be about 6 emeralds for 3 bookshelves, and another trade with 4 books for an emerald. If the villagers like the player enough, they will discount the trades. In my case it made the trades 2 emeralds for 3 bookshelves, and 1 book for an emerald. Making it an infinite loop of trading.