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

Even the 1tb ones cost too much now. What, are data centers using those too??

Transferred demand.

SDDs and HDDs are too expensive, so people are using SD cards instead.

I think it’s more that the companies producing flash storage have shifted their focus to ssds and therefore lowered the supply of SD cards ?