I think some of his asking prices for subs are a little too high. Actually owning some 80's-90's subs, I can tell you that they are night and day from what is offered nowadays. Completely different animals. Older subs were built when big power would have been 250 watts to a single sub. So, they were more efficient and power sensitive. And the build quality was just OK, not superior in most cases.
I like and use the older V1 and V2 Image Dynamics IDQ subs from back in the day. So, I guess the market is there. But, I do USE those subs. There are some people who will pay a lot for nostalgia pieces that they can sit on their shelves and brag about owning.