When I cured a zombie villager once, it gave a discounted price (in this case, 11 glass panes for an emerald to 4). However, when I went to infect and cure it again, it didn't lower the price, even raising it to 5 glass panes per. I am using a Skynode Server for 1.16.4, so it might be an issue on their end, but I could not find any documented instances of this. The images demonstrate this issue with villagers cured both once and twice.