You don't remember when GTX 1080 Tis could be had on eBay for as cheap as $400-$450??

Because I sure do... I should have bought two. Now you can sell one - today, right now - for $700-800. I haven't seen an auction with a final bid less than $650, and I've been watching. Most "Buy It Now" options are $700-800, and aren't having all that much trouble selling.

We're talking two generations old cards, released almost four years ago, that are selling for what brand new GTX 3080s are supposed to MSRP at.