In my friend's Realms world we are playing, I have many villagers put in small locations with their respective job item beside them. No matter how much I trade with them, after logging off, their prices will return to normal, as if they had just been given their job. As an example, I trade 22 Nether Warts with my cleric a few times, they lower the price to 21, I take advantage of that, log off, come back the next day, and prices return to 22 Nether Warts per Emerald. This also happens for my other types of villagers and their prices. The attached image shows the price when it's lower, but it will always return to normal (as with the rest of them) once everyone logs off for a few minutes.