That's a fantasy. Used will sell for whatever the market will bear. It's a discount from new, but seldom 50% off.
Often pricing is delusionally high. I checked the "local" used GPU market on Kijiji. There was nothing I would consider a reasonable deal. Several people were trying to sell used 5700 XTs for $500 CAD. RX 6650 slightly outperforms it, and have been continuously available for months at $400 CAD New or less. I wonder if anyone actually finds suckers for their used cards at those prices.
-I think there is some timing that goes into it, and there is a certain amount of "absolute" or realworld savings to consider.
Right before the 4090 release I snagged my 6800xt for $400 since folks were doing the usual panic selling while new cards were still going for $700. Although it's not 50% off new, a $300 savings going used is really tangible.
The major issue right now is the new gen cards kinda suck, so older cards are retaining a disproportionate amount of value. If a 7600 performed like a 6700 at $250 or a 4060ti performed like a 3080ti for $400 there would be a huge downward pressure on older used cards but that's just not the case.
You're not wrong about pricing still being delusionally high, and I place the blame on the buyers more than the sellers in this case. Do none of them know how little more one of these cards would cost new with a warranty and the whole shebang?