>A raspberry pi is $25 and far exceeds the home computer of the 80s and most of the home computers sold in the 90s.

That would be relevant if the metric was "cpu power of computer sold in the 80s".

There were some $100 (or even $25) pieces of hardware far more powerful than ENIAC in 1980 as well.

But the relevant metric is "cpu power appropriate for contemporary uses and programs" -- and in 2018 it means what people in 2018 consider a home computer.

>If your goal is just learning how computers work, you have far cheaper options today.

Why would that be your goal? That's only of interest to programmers and tinkerers, not 95% of the population.