there was a sell off phase as asic Bitcoin miners started taking over the Bitcoin market. rx480's were still new ish & nicely cheap, selling second hand significantly under $200.
but all sorts of other currencies arrived & have kept inefficient gpu mining going. alas.
I do feel like there are more reconnings coming. it will make for cheaper gpus. much more squeezed market prices, a need for gpuakers to be more competitve. to really deliver new value with more recent chips.