As the prices of Ether and Bitcoin return to normal, GPU mining is no longer as profitable as it was in 2020 and early 2021. As such, miners have started getting rid of their equipment while they still can. This is doubly true for Chinese miners where the government has placed harsh restrictions on large-scale mining farms.
I wouldn’t exactly call these prices “affordable” just yet though. Most of these second-hand GPUs that have undergone intense work-cycles over the last 6-12 months are going for close to the MSRP, generally a tad bit over it. For example, the GeForce RTX 3090 is available for 12,000 to 15,000 Yuan ($1,800-2,300), a fair bit over the MSRP despite being a second-hand or perhaps, third-hand product in reality.
In addition to the newer RTX 30 series (Ampere) and RX 6000 series (RDNA 2) graphics cards, there are plenty of older Pascal and Polaris parts on the second-hand market as well. The GeForce GTX 1060 and the Radeon RX 470 and 480 are some noteworthy names.
I wouldn’t recommend buying a second-hand GPU for the price of a new product (used for mining or otherwise). It’d be best to wait for the holiday season. Prices should stabilize by then, and you will probably be able to buy graphics cards and CPUs for discounted prices too (if you’re lucky).