High-quality gear that is well maintained will hold its place in the market. That the market is unpredictable is the problem. I paid good money for a lightly used Hasselblad system about 7 or 8 years ago, and I watch the KEH prices on occasion to see how the value is holding up. Given that I use the system, its value as I perceive it has held up pretty well. I probably would ask about 85% of what I paid for it if I was to sell it privately today. I figure any decline in market value is fair given the amount of use and enjoyment I get out of the system.
This strategy of buying good quality and holding/using it for a long time has its faults, too. Just ask me about my Canon F1 and FD lens investment from 30 years ago. They all still work, but resale value is a small fraction of what I paid. I wouldn't feel so bad about it if I actually used it any more.