As the title says. When curing a zombie villager (no matter how many times you cure it, it can be once or twice etc.) his trades drop just as usual but after a certain amount of time and trades he suddenly increases his prices to about double the regular cost.
e.g. 20 paper > 1 emerald turning into 20 45 paper > 1 emerald
And this is happening randomly so sometimes even turns back into a more accurate cost taking the conversion from a zombie villager into account.

To make this clear, I never met any of the requirements to ever drop my popularity that'd cause a increase of prices.

Added to this villagers now seem to actually restock only about twice a day instead of around 8 times just like in 1.14.4

EDIT: When they drop their prices it doesn't drop to exactly the same amount meaning after multiple times of this happening it's like the conversion never actually dropped the prices.