I have a small server with only 5 players on it. Each of us have our own cured villagers for enchanted books. We noticed today that their prices sometimes bump up a bit (Ex. An unbreaking 3 book was once 1 emerald, 1 book, but it bumped up to 2 emeralds 1 book)
Can't find any reason for this, we don't push them out of bed, hurt any of them or their iron golems, and they can all socialize.

Is there a reason for this? Or is this a bug?