What is something that's crazier than the wildest dreams of any ~1970s nerd, but exists today? I'll start with an easy one:

and yet we are told that it’s too hard/expensive to add a 16 gb Video Cache to a consumer graphic card.

Uhh very, very, very different type of memory. You could try using a microsd card if you’re happy with 10 spf I guess, I prefer measuring in fps though

10 spf is too low for me, I’ll sunburn