Just a thought tbh.
3/20/20's can fluctuate but will likely never drop in price much short of mass duping. Their drop rate is abysmal and many are needed for a good mellee char. In the past I have often used one or two off from perfect due to how much cheaper they were while functionally being the same like a 3/20/18 would be greatly cheaper and the difference negligable.
In the past the last big crash I saw was in version 1.10-whichver patche ended easy duping. I had a few legit 3/20/20 charms given to me then, and a crapload of imperfect ones I found. The permed/legit ones then were something like 40-60 high runes each, while duped ones were something like one mid-high rune each, so guess what the masses used. This was at a time when a legit soj was worth ten times what a duped one was because it would not poof, duped imp shanks on use west equalled 40 high runes and were used for trades because runes were so mass duped inflation hit and values exceeded what could fit in the trade screen, legit imp shanks when for some ungodly value but few traded them due to rarity.
So if mass duping came back yes you could see a crash as 40 duped charms would cost a fraction of a single legit one.