> They are also not top of the line gpus... which gamers want to buy. older rx470 polaris class gpus are more than enough for large mining farms.
Way off the mark there, gamers not in the 1% don't buy top of the line GPU (as reflected in the Steam survey), they buy the budget to mid range price. When miners started buying GPU left and right in pallets, NVIDEA and AMD saw it and shift the manufacturing to the top of the line GPU where they have the highest margins even if the waffer would yield a lot less, because miners would buy them ASAP anyway. This reduced the amount of lower tier GPUs in the market.
Funny you mention the RX470, a GPU famously never in stock because of this dumb piramid scheme.