I make a fletcher villager to make he buy 1 stick for 1 emerald from 32 sticks by convert him to zombie villager then cured him several times. After stick prices goes down to 1, i make him once again to zombie villagers, then quit the world and enter it again. After i cured him, the price goes back to normal (it discounts to 26 sticks like i just cured once time).

I speed up the curing process using command:
/data modify entity @e[type=minecraft:zombie_villager,limit=1,sort=nearest,nbt={ActiveEffects:[

]}] ConversionTime set value 0b

Even though without that command (it will take about 30 minutes), the villager still reset the price while re-open the world while he is still zombie villager.

Original video https://www.youtube.com/watch?v=ejnFo7dj6kU