Not only was I affected by hero of the village, but in addition to that, I had also gained some discounts from trading with the villagers. even with these both in my favor, I had no discount whatsoever. the UI deceived me into thinking I would pay 6 emeralds for what would usually cost 31 emeralds.  Much do my dismay, I was still charged 31 emeralds. The villagers have not given me a single discount on my world, with our without the "hero of the village" effect.