I don't think that's quite true. We had Heath kits and a lot more variety of computers from the late 70's to the early 90's. There is no under $200 computer sold at major retailers like there was in the 80's.
* Well, there is a perfectly rational reason for that, and it is not really a problem for hobbists. But that's the fact.
There are LOTS of under-$570 computers sold at major retailers today.
$570 is a lot father out of reach today for many than $200 in the 80's.
It's unfair to say that they don't get cheaper considering that a Mac Mini is an entirely different class of machine from an Apple II, in so many ways that it's ridiculous to even try to list them here.
As for your statement about $570 vs $200... what do you base that on?