The scalpers are still lurking around? How about them to lower the price to 50% of a brand new card?
Who knows if that "second hand" actually works properly and how many mining hours it had been tortured.
I sold 24 mining GPUs on ebay in March, and I sold them with a no-quibble 12-month warranty backed at my own risk, and enforced by ebay
So far, 7 months in zero returns - nobody has even contacted me. I reckon I sold each card for £25 more than other cards listed simply because I had the confidence to offer a warranty.
I sell my gaming cards without warranty.
ETH mining (done by careful miners who cared about the hardware, efficiency, and their resale value) looked after the cards way better than any gamer would. Regular dust cleaning, careful 24/7 thermal monitoring, open-frames for exceptionally low operating temperatures, undervolted, GDDR6 temps lower than when gaming, and stable unchanging temperatures that meant it wasn't thermal-cycled like a gaming GPU is. My gaming cards get put in a box, never cleaned until they're replaced, and their workload is bursty resulting in frequent temperature and power spikes from idle, in a hotbox, with tons of thermal-cycling on the GPU die, the VRAM, and of course all the thermal pads.
The only caveat to a well-treated mining card is that the fans have been on their whole life. Given that their 24/7 TDP was around half of a gaming load, the fans were running fairly slowly so unlikely to be ruined, and you can replace GPU fans affordably and easily for most models.
AMD's Rx 6800+ series all have 16GBs of RAM though, which is very useful for compute applications.
Which "compute applications"? It's nice in theory and I wish CUDA would die a horrible, proprietary death in favour of Opensource APIs, but the reality is that most software developers hook into CUDA.
I've been building and maintaining both CPU and GPU render farms at work for nearly two decades (well, one decade in the case of GPU rendering) and support for OpenCL is hot garbage. The API may be okay but most software wants CUDA so it doesn't matter how much RAM your Radeon has when the application only offers CUDA or CPU compute options. I'm coming from a 3D rendering/animation/modelling side, so perhaps financial/physics simulation software does actually have decent OpenCL support. I can only comment on the stuff my company does.