My first thought when reading the title was that these scalpers are delusional, since nobody is going to pay as much as or more than a 4090 for a 7900. So much for that. Some people just have too much money and/or not enough sense.
With an impressive US$5,000 bid on the limited edition Powercolor Red Devil 7900 XTX in an auction that will end later today, eBay has quite a few less expensive video cards based on AMD's latest GPU. Sadly, the reference RX 7900 XTX design with its list price of US$999 is far behind the custom cards listed on eBay.