Out of curiosity, I watched an auction of a Nikon D810 (because I own one), it sold for £549, that's a camera that six years ago sold for over £2000. In the very early 80's I owned a Nikon FM2n film camera, I think I paid about £110 for it (although I'm not entirely sure and some 23 years later I sold that camera on eBay for, yes, £110. Ok there is inflation to be taken into account but nevertheless, that was good value. When I see things like the D810, it makes me wary about spending on new camera equipment, especially the actual camera. Even lenses don't really hold the value that one might expect although I'm not sure why. Manufacturers come out with new models all the time and second hand value of the previous one plummets -- yes that is the way of the world I know.
Take the Nikon Z7, when released it cost not far off three grand but was superseded by the Z7ii a tiny bit over two years later so second hand ones now go for a little over a thousand; that's a big drop.
Fifteen years ago, I bought a Yanagisawa saxophone for two thousand pounds, with the right climate for its sale now? about £2000, despite one new model being introduced in the meantime -- that is my only asset. Oh, apart from my tiny house which I bought 20 years ago for £60K and is now valued at £235K - should have bought two!
It all makes me wonder if there is any photographic equipment that holds its value for years or should even the highest quality gear be, in the end, considered disposable.
