Balancing the villagers

The game has such a problem: The game has become too easy on the endgame.
Therefore, I propose a partial solution to the too simple endgame.

In this post, only the villagers are described, but the problem is not only with them.

• There must be a limit to the discounts for villagers. This will fix incorrect discounts, for example: when you buy a bookshelf for 1 emerald and then sell 3 books that fell from it for 3 emeralds to the same villager. 

• Librarian: No longer sells an enchanted book at the Novice level. But also added the sale of an enchanted book at the мaster level. This will fix the endless and free change of 1 and the same villager in search of such valuable books as mending. After that, in order to search for such valuable books, you will have to trade with each resident in order to see what books he has to offer you.

• Receiving diamond products through villagers should be balanced. There is literally no point in digging diamonds in the game right now. It is cheaper and faster to buy a full set of diamonds from the villagers.

Possible solutions:
Add the need for diamonds when purchasing diamond items from a villager. For example 4-6 diamonds and 21-35 emeralds to buy a diamond chestplate.

A separate type of armor, weapons and tools that will be worse than the diamond version, but better than iron version. And to make it so that it could not be done, but could be bought from the villagers. At the same time, diamond items will no longer be sold by the villagers.