I came to 3080 from an EVGA 2080Ti Black and an EVGA 2080Ti FTW3.
I got my 3080 EVGA XC3 Ultra on launch morning.
My 3090 FE is in the mail. But I will sell it towards a Kingpin because I want the built-in, warrantied AIO cooler.
#1. Regardless what people say, both of those cards are 1080p and 1440p beasts. If you are playing on a 1440p curved gaming monitor,any 2080Ti is still worth whatever you paid for it.
#2. People who got suckered into selling their 2080Ti early to avoid depreciation and ended up with nothing due to the 3000 debacle lost most of their value.
It is smarter to ensure your auction on EBay ends late in the launch day of the new product so that you can terminate it if you fail to get the new product- avoiding negative feedback.
#3. The 3070 will “hurt” 2080, 2080 Super and 2080Ti used prices but the key is: the 3070 will face the exact same instant buyout that the 3080 and 3090 did.
If you have nothing at all, you ain’t playing anything at all.
So to answer the question: “what’s your GPU worth”, the answer is: “whatever the free market is willing to pay for it”.
2080Ti prices fell on speculation prior to the 3080 launch, but rose right back up after the launch.