The second hand market is probably a pretty thin market in the scheme of things, so it's more prone to distortions. Most people probably buy a GPU new and then use it to the point they either give it away, trash it, or set it on the shelf collecting dust. In other words, there are certain people willing to pay a lot for these cards, but in terms of the overall graphics card market it's likely a drop in the bucket.
To be completely honest with you, if my GPU died and could not be repaired I'd either just play old games or do something else rather than pay the currently inflated prices. I wasn't willing to pay $1500 for a 3090 when that was the legitimate MSRP. I'm certainly not going to pay that much for an older/slower card. Doesn't matter whether I could "afford it" or not, I'm not going to pay rip-off prices on that level.
