Just watching it happen in real time, I'm reminded of the WoD days. Even at the rate a few garrisons produce mats, it wasn't enough for crafters. Ore was still being bought and used in piles even in the last few weeks of the expansion. It was amazing to watch, piles of crap goes in, gold comes out, repeat. What I'm seeing reminds me of that, I'll list some mats picked up during casual play and it's sold in minutes. Dragonflight seems like it's going to be crafting heavy, so maybe we'll have another WoD situation where mats pour out of every cupboard and there's never enough.
I did notice a slight drop in situation specific stuff. Like old mats for vanilla legendaries went up a bit, unused AQ40 scarabs/idols went down a bit.