Unreal prices

"Its the uneducated that are driving up the prices on those units!"

Why uneducated? People want what they like.

It is not ignorance. It is a blissful ability to buy what one wants.

Old and rare and durable are nice. IF not since supplanted by objectively superior products. Only discontinued legends I would crave are non-electronic, and almost all non-mechanical. The exception would be Mouli manual tin rotary cheese grater. When it comes to grating the Parm, steel sucks, stannum rules. All others are kitchen and garden hand tools not since matched or replicated, much less exceeded. You'd have to pay me to take an old Pioneer receiver. Put it in an effing museum.   

Pioneer had some of the cleaner looking receivers, design-wise, and great FM stereo receiver performance...their separate tuners are pretty classic, but like most of the Japanese products from the mid-70s, the integrateds & receivers' preamps were not up to the amps IME.  An H-K 930 sounded better than the equivalent Sony, Pioneer or Sansui of the day.  But consistency and reliability went the other way.  Yamaha and Tandberg made better balanced, better sounding stuff than most of the "usual suspects"...all this before "high end" audio was created by Mark Levinson and ARC.

Just last week sold my 70,s Sanyo JCX2400K receiver that was the hub of my second system which I decided to dismantle.
I know what I paid for it and listed it on eBay for a goodly amount more than that figuring somebody would make an offer sooner or later.
Darn thing sold in about 3 hours at my asking price.

Sanyo was very overlooked in the Japanese hifi wars and considered to be the poor relation.
This thing was built like a tank and everything worked and sounded pretty good to my ears, loved the tone controls, filters and loudness switches etc.
Somebody should be happy with their new toy.

Open your eyes, this is perfectly normal. Yet for some reason everywhere I go its always the same. The people who should know the most turn out to be the most oblivious. So let me explain it to you.
Its not that the receivers or whatever are so great. Its simply that they have endured. Whatever lasts and is kept in good condition, it hardly
matters what it is, its value will increase over time.

So well put!!! I still have a few pieces of audio equipment that are 
working as good as the day I bought them, without ever having to have them so much as serviced.  Craftsmanship shows not only in detail but as you state, in the ability to endure the test of time.