On my friend's minecraft realm, I would occasionally heal zombie villagers, and one or two baby zombie villagers, and get extremely cheap trades for specific items. The only problem I've had so far is the farmer villagers. They offer me trades of 1 pumpkin or melon for 1 emerald. I've done them quite a lot, but recently the numbers have stopped making sense. The GUI still says 1 pumpkin/melon for 1 emerald, but when I trade with them it will take a significant amount more than just 1 pumpkin or melon.

For Example:

The basic trade (without discount) is 6 pumpkins. The GUI still says 1 pumpkin but when I trade it takes 8 for the trade to work. When I do 6 trades, it should only take 6 pumpkins, maximum 36, but it takes more than that.

Even if this cost change was intentional, the GUI still has not changed to tell me the correct amount.