A relevant topic for many of us. My system is comprised of equipment all purchased used, so I have a keen interest in the used market.
Observations:
Mac and Marantz markets are unique and continue to rise, with as many speculators as there are enthusiasts involved.
In general and for most speakers, value is inversely related to size and weight. Large and heavy ? I’ll pay you to take them away. Small, light prices are steady. Exceptions- Horn speakers both vintage and relatively new. JBL and Klipsch horns are viewed as legacy products and hold value. Vintage coax and triax like Jensen and Tannoy hold value. In the non horn realm, AR3 and AR3a hold value.
"Meters" are considered old-skool and the perception (correct or not) is that anything with meters was better than most when new, so the assumption is that meters = higher quality and they look cool.
There is nostalgia driven demand for silver faced equipment from the 70’s and 80’s- the equipment that 12yr old boys drooled over in catalogs and stereo stores, but could not afford at the time.
Vintage tube equipment holds value and is steadily rising in value. Dynaco has plateaued. Fisher and Scott continue to increase. Sherwood and Pilot are slowly improving. Heathkit and Eico are both rising and falling. Higher end designs continue to rise in value, cheaper stuff not so much.
What surprises me most is the CMV of Conrad Johnson and ARC equipment from the 80s to early 90s. These components were very well made, sound a lot better than "vintage" and give up very little to current models. Yet prices are almost pocket change ! You can set up an outstanding CJ or ARC tube system for about $2500 that would cost you about $10k to match using new equipment. ARC SP6 or SP8, paired with a D70, or CJ PV5 or PV10 with a MV45 or MV50. That said there are specific models that continue to rise in value, ARC SP3a, ARC SP10 come to mind.
Luxman tends to have low resale prices. Japanese vs US pricing is an issue for new and recent models. One can purchase directly from Japan for 50% less than US pricing, and that affects used prices if one wants to sell. Older Luxman sounded great, and was well built, but prices have lagged in the market. Older Luxman tube models seem to be very cheap relative to performance. Which would you rather have, a rebuilt Dyna ST70 or an EL34 Luxman amp for the same price ? Which would likely sound better ?
There are still deals to be found- just keep looking. Also- a key to selling that most do not understand, is that online sales are visual ! Take the time and put in the effort to CLEAN then take multiple well lit and high resolution pictures of what is offered. You would be surprised at how many sellers take a few cell phone photos of a dirty piece of equipment located in a garage, or just purchased at an estate sale, then add a price that they think will allow them to retire. Dream on. When I sell, I take pictures from all angles, and open up the piece to to the extent reasonably possible so I can include detailed pictures of the interior.