Universal Coins Mod is mods for minecraft 1.8.9 allows you to trade almost any item using coins. The coins come in five values: the Coin (value 1), the Coin Stack (value 9), the Large Coin Stack (value 81), the Small Coin Bag (value 729), and the Coin Bag (value 6561). Obviously, 9 of a lower tier will get you 1 of the higher tier; also 1 of a higher tier will get you 9 of the lower tier. The trading is done at an Universal Trade Station. The only way to get coins is by selling an item. Most vanilla items have a predefined price and prices can be changed in the pricelist files.
Download link: Universal Coins Mod 1.8.9/1.7.10