The price jumped up a ton from when you bought it.

https://www.amazon.com/Nvidia-GEFORCE-GTX-1080-Ti/dp/B06XH5ZCLP

https://www.amazon.com/EVGA-GeForce-Founders-Support-11G-P4-6390-KR/dp/B06XH2P8DD

​

https://www.ebay.com/p/16026507463?iid=123919351872&rt=nc&thm=1000

The used ones are 500, but the pages literally say that they are almost out of stock. Even the new ones are 800.

Nvidia is a freaking monopoly that needs to get split up to bring back competition, lower prices and innovation. But that's an entirely different thread on its own.