I managed to obtain a 2 emeralds trade for bookshelves on a cured villager, the default pricing is 3 emeralds but it seems to go down by messing with the demand/supply system. (I was just looping the trade to level him up, a while before I had bought the enchanted books)

2 emeralds for the bookshelf, 3 books, resell the books, get rich

Note that another cured villager is working near this villager.

Edit: redid in creative and the other villager wasn't needed