Userbenchmark is NOT a good site to compare performance. It's only good to see if your systems runs ok or with an issue. I would NOT suggest you to trust those results.
and what it offers - GTX 1080 Ti - 11GB!
The card had often guarantees 5 years
- and I can buy it with warranty min. 2-3 years.
You will be buying OLD tech that will not be supported as long as the brand new 3060Ti. Also it is almost impossible to max the 8GB of VRAM in Full HD (1080p). I game at 1440p (higher res requires more VRAM) and the most I have used so far is 6,4GB in a modded game.
Core clocks can't be compared between different generations or between cards that have different amount of Shading Units, Tensor Cores or RT cores. There are different architects built in different manufacturing process and using different power draws. It's like comparing 6000rpm in a Fiat 500 and 6000rpm in a Bugatti Veyron.
To sum up... I'm thinking of buying with models:
- GeForce GTX 1080 Ti / GDDR5x - mainly by the 11 GB, GDDR5X, and 352-bit / Core Clock 1481 MHz/ benchmark / best priced- I don't know what company yet - from £250.00 to £330 - Ebay
- Palit RTX 2060 Super JetStream / GDDR6 or RTX 2060 Super/ GDDR6 - best priced
- GeForce RTX 3060Ti / GDDR6 - I don't know what company yet
So now, you want to buy not new, but from ebay, so no warranty again...
If you only care about one game, just watch a youtube video with it played with a 1080Ti and with a 3060Ti.
About the prices, I agree, it's expensive right now but it will begin to normalise soon. If you can't wait, pick whatever you want that's within your budget.