Interesting discussion here. I'll try to add my thoughts.
First, a playable instrument has a certain utility value that equals a certain amount of money. Then there is a collectable value on vintage and high end instruments. Then over and above that there is a luxury value on quality instruments built with nice woods, fancy construction, etc.
Take an old Fender bass. By and large many hit recordings were made using a fender bass years ago. A lot of them sounded very good. In fact, without Fender, I doubt the rest of the bass market would have grown, including Alembic. That quality of sound would be it's utility value. Despite what you may think about a Fender, the bass does the job and does it well.
Then there is the rarity of the instrument, plus it's iconic value, plus it's investment status. That is it's collectable value. Old Fenders rate very high, partly because they are recognizeable symbols (like a harley davidson).
Then there is the luxury value. Although Alembic is crafted to a high luxury value compared to a Fender, old Fenders really are luxury items. Why else would anyone pay 6K for a 60's model when a new mexi jazz is so cheap and still sounds good?
Also, I think many folks wanted a Fender bass years ago but could not afford one, which makes them also desireable for a generation looking to re-affirm their life via nostalgia items. Alembic was not known by and large back then, and was not in business in the fifties.
Alembics are icons of a generation to a few folks who recgonize them from a few groups who used them. I am always surprised at how many responses that any posting on this forum that mentions the Grateful Dead will get. Or the Who or Led Zepp. However, there were a lot of other groups out there making music back then.
I like the car analogy. For instance, I would eguate a old Fender P bass to a 65 Mustang rag top. The Alembic would equal a 70's Porsche mid range 911 to me. Old Mustangs convertibles are worth a ton of money, old 911's really aren't, despite being much more high performance. However, a driver wanting to go fast would still pick the 911 for it's utility value. They would pick the mustang (at this time) for it's collectable value. In terms of luxury, the 911 was more upscale, but the Mustang is very much a luxury item in terms of something that is not a necessity. Of course, the Mustang is an icon and a great investment.
Just my thoughts.
Dave