Apparently you can install Linux on the T2 chiped apple computers, just not by default.
https://www.omgubuntu.co.uk/2018/11/apple-t2-chip-cant-boot-linux
On the price issue, a large factor into the cost is die size. The RTX 2080 Ti coming up 775mm Sq. vs 471mm Sq. of the 1080 Ti. Which is approximately 60% larger, I could not find the die size of the 2080 (in a very quick search, didnt try to hard) but it safe to assume it is larger as well...
Then you didn't have something configured correctly. I have beaten RotTR, Deus Ex: Mankind Divided: well over 1000 hours of War Thunder, Company of Heroes 2, Pillars of Eternity, about half my Steam library is linux native. I have even played Battlefield 1 in wine with DXVK online. Its not at...