This stuff was worthless not too long ago. Just like the '60s and '70s muscle-cars that went to the crusher. I'm pretty sure they made at least 50,000 (probably many more) SX-1250s, probably 100,000 or more each of less expensive models of the SX-x80 and SX-x50 and they're for sale every day on evilbay, ... thousands of them are still in attics, garages, basements. I love owning and restoring them, even more I love looking at and listening to them but lets face it, they're not Faberge' eggs or the Hope Diamond, ... people don't know we're out there looking for them.
More recently those of us who want to lovingly restore the and re-live the glory-days are creating a demand, which has increased the prices from nothing to ridiculous.
Not everyone knows that there is a collector presence out there or wants to be bothered to sell it.
I had to throw away a one-of-a-kind custom made by Kelvinator circa: 1920 refrigerator when my Father sold his lake house several years back, some vintage outboard motors, other stuff. When the new owners are taking possession soon and you need to get his stuff out (of 11,500 square feet) you eventually give up on finding a place for this stuff and throw it in a dumpster. My Father's old stereo went to my son though, ... that part was easy! Sansui, Teac, Pioneer, ... This was 2000, it was his summer house that sold for $2.5mm, he wasn't that concerned about whether he could spend a couple of days in his golden years finding a home for something he had in his attic for a decade or more.
The same happened when my Grandparents passed: my Parents and their siblings moved most of what furnished the house to a pile in the garage to be picked up by Salvation Army, other things trashed, only the really nice things with significant value became "inherited". I don't know where the stereo went but they weren't worth anything in 1988.