> How so? Computers haven't been prohibitively expensive since what, the 80s?

Initially they weren't, which is where we are in terms of a maturity model. Most technological improvements are initially prohibitively expensive to obtain (even if they are cheap to make) because of Jevon's Paradox. This is my personal understanding, which may or may not resonate with others.

FYI there is no academic rigor to "Jevon's Paradox" and makes a lot of wrong assumptions but it's cute when a billionaire finds a new term to use to excuse their poor behavior.