I cured a zombie villager on my realm world yesterday.
When I logged back in today the price reductions were gone, at least visually. I haven't tried actually trading yet.
Possible causes could be:
me logging out
a time out
an IOException
(Sorry I don't remember the exact way the two last ones were phrased)
These are the three only events that happened since yesterday.
Duplicates MC-154929 (Works as intended).