[Arran]

There is one huge difference between stereo gear of the 1960s and 70s verses the so called "Muscle Cars", the "Muscle Cars" were originally purchased by younger buyers, usually in their 20s or 30s, and then ended up being sold second and third hand to still younger drivers. The ones that didn't end up getting crashed by their original owners ended up getting driven into the ground by their second or third owners.
I'm not sure if the same could be said about high end stereo gear in terms of target market, it was generally marketed towards anyone who had money to burn. Also most stereo equipment of it spent it's life inside and was used but not abused, muscle cars by their very nature invited abuse, drag racing, speeding, etc.
While there is a nostalgia craze right now for stereo gear, there also used to be for transistor radios maybe 15-20 years ago. With the transistor radios so much of it came out of the woodwork that now only the early and rare sets get anything above three figures. This doesn't mean that the audio equipment will go the same way, but unlike transistor sets they take up more room, and if it doesn't work there isn't really much to look at.
Regards
Arran