Think you need to revisit what 20k means. The previous 2 peaks were 16k that’s a 20% drop off from 20k. Keep in mind there is a large bot population too.
Take money from the entire server and put it into a few companies pocket that give them millions a week for many months. Those companies in turn can buy out markets and roll all the armor they want to and drive up BiS gear sales well over gold cap while average players are lucky to get a piece of gear before it changes to not so good anymore.
5% of the server does more than 25 dungeons a week… oh crap we better put a cap on this as we dont want them to get ahead. There is nothing to get ahead in but umbral shards and who cares.
I think they should eliminate the limitation, the more mutations they can make, the more threshold they will have available, therefore the price will drop and it will no longer be “so” profitable for gold sellers. And they should make it available to sell in the formal trade.