Thanks. What I still don't get is: Are there suddenly like 20 million miners or what?? I could understand if there was a shortage of video cards for like a MONTH or something... but it's been almost a year. I really can't imagine that so many people would need... every video card on the market... for mining.
It is hard to get exact numbers for this sort of thing, but we can imply it from stats available. I'm only looking at Ethereum which remains the biggest GPU mineable coin. Current network hashrate is around 615 TH/s. A well optimised 3070 is around 60 MH/s. In other words, the current work being done on the Ethereum network is equivalent to 10M well optimised 3070 GPUs. In reality, you can be sure many of those will not be best optimised, and also people will be using more lower cards than those using higher cards.
Power efficiency is notably improved with each generation. Ampere is better than Turing, is better than Pascal. Not exact, but Ampere is ball park 2x as efficient as Pascal. Better efficiency = better profit. More GPUs = more profit potential. If you have the capital, it scales that simply. As long as crypto value remains high enough to make small scale mining profitable, many GPUs will be going to mining. If it dips, then that could reduce the pressure to only those who are in it long term vs short term.
BTW I just crunched the numbers since I may have to declare my mining income to the tax man. My mining income this year so far, of which I've only been active for about 4 months, is near enough £1000. The bulk of this is 3070, 2080 Ti, 2070, with some Pascal era cards added in when I wanted more heating. It is hard for me to give an exact running cost since I turn GPUs on and off depending on what else I'm doing, and this is strictly on the side for me. Worst case GPU only electricity cost assuming I ran all Pascal era GPUs and faster is 25% of my income.