You can't just see inflated prices at the high end. When that happens, actual consumers who just spend in a particular price range get forced down the stack and the who problem is exacerbated by shortages. The actual gaming market is getting pushed down the stack and increasing the demand for these low-mid and low-end GPUs.
I just pulled up a website that calculates hash rate and expected profits and RVN is roughly half of ETH. It'd take over a year to get a return on initial investment even with inexpensive electricity on some of these low-end cards and that's probably a bit long for many miners. If everyone gets pushed to RVN suddenly you've got more miners competing which drives down profits even further.
ETH has a market cap almost 500 times larger than RVN. It's impossible for any other coin to absorb all of that without seeing some drastic market fluctuations. The uncertainty is going to lead to people wanting to get out, especially if they've already gotten a return on that initial investment.
Long term you may be correct and we'll see GPUs get absorbed by miners again as new PoW coins emerge or as existing ones grow to fill in the space left by ETH moving to PoS, but it's going to take some time for it to reach that point again.
You dont understand, if ETH indeed goes down, people is going to switch to mine diferent alt coins, you are betting on the next big thing, and it is best to mine as much as possible early on. Thats why 4GB gpus never went to the used market, they are all mining alt coins. Even if you are mining at a loss.
People that want to get out are the poeple that, a few years later, will sorry for that decision. A little history lesson is in order here... BTC went to ASICs in 2012-2013, people went to mine alt coins... most of them worth nothing today, but who mined Litecoin and Dogecoin ended up winning big time in the long run.
What will happen is that will be far less demand for NEW gpus, just dont expect to find cheap old gpus. Also the gpus that will show up first will be the worthless ones, like the RX 570 4GB, GTX 1660 non super... that might as well be IGP-level by 2023. Hell, due to memory limits all 4GB gpus have a chance to be IGP-level by next year.
(thats also why i want to see RX 6400 perf, thats petty much RMB IGP, but with a 16MB IC, but RMB has 8GB VRAM, and the RX 6400 is limited to 4GB)