Not usually, no. They usually use custom designed chips, either ASICs or FPGA chips, not GPUs. Depends on what cryptos are being mined and what hashing algorithm they use. A lot of people who already have GPUs for games or work use them to mine with, but that's a lot different than the claim that mining outfits are buying them at 3-4x MSRP for mining. To give an example, I have a 3090 (which I signed up and waited months for) and don't use it to mine with, because it would net me a whopping $200/mo if I ran it 24/7, which is not including the costs of cooling my room down and the extra electricity. So it would take about 2 years of constant mining to break even on a card I bought for it's regular retail price. If I had bought it for scalper prices of $4k, it would take double that. That doesn't factor in difficulty changes though, which this year in the last 6 months have doubled, cutting the rate of return by 50%. So if that holds true, it would *never* break even even at retail price, much less scalper prices (since by the 6 mo mark from now, it'd then take 3.5 more years to hit break even, then in another 6 months it would take 7 more years and so on). The fact of the matter is, GPUs are attractive for mining only to people who bought them for some other reason, and most won't ever break even on the cost of them. Which is fine if you'd have bought one anyway, but makes little sense if you are trying to run a mining farm. Factor in other overhead costs and it quickly becomes a non-starter for anything more than a way to make a few extra bucks.