Location makes a lot of difference here. In parts of the world where there was simply no money or market for devices when new, and where there was no big 2nd hand market when still current, things will tend to be unobtainable. The bigger the reach of a sales platform, the higher the total demand and so the higher the prices will be. An object sold on eBay with shipping anywhere in the world will inherently be more expensive than an object sold on the same platform with limited shipping, and that in turn will again inherently be more expensive than something sold on a specific local platform. The flip side is that it can be very difficulty to find, buy and get delivered a lot of stuff on such local platforms, and that those difficulties tend to correlate strongly with the price difference. If you're located in a country most people don't want to sell to and/or ship to, you're going to pay a premium.
Bottom line: it's better to live in US, Japan or EU, and if you live in unrecognized states or conflict zones, you're royally screwed, with a broad spectrum in between.
Take Roland stuff. There are a few pretty universally sought-after models (i.e. MT-32 and SC-55). They were expensive when new, so never really widely sold - but those that were ended up disproportionately in Japan, with the rest basically being in US and EU. If you're now living in for example Brazil (somewhere the devices probably aren't available locally, but otherwise not a hugely problematic country in terms of payment or shipping), you're stuck with sellers with global reach and prices to match. In Japan though you could probably find the same stuff on local classified ads for a fraction of the price. It might be possible to buy remotely using a forwarding service (something I have done to get a Roland A-880 MIDI patchbay from Japan for less including shipping than the few that turn up in my corner of EU locally, let alone what one would cost on eBay), but that only works with some ads on highly automated platforms. For every device there, there's one on a piece of paper an old lady put up in a supermarket somewhere, or one in a car boot sale or attic clearance. Probably somewhere in Japan in this case. Whoever sees that, gets the device for the really nice price, and unfortunately chances of finding this sort of thing is not fairly distributed across the world.
So TLDR: what something's worth to me need not be the same as it's worth to you, even objectively.
Then subjectively... personally I won't spend really big money on old computer hardware; part of the fun for me is digging up nice bargains, buying a box of 'old computer stuff' and sometimes getting lucky (frequently less so, of course). Same goes for building systems, the compromise involved with not just shelling out for the 'perfect' parts is a significant part of the experience. So I'm not the one driving up the price of that V5-5500. I might however one day find one in an old box I paid maybe EUR 10 for. That's how I got my V3-3000 PCI after all, and my Apocalypse 3Dx was in a battered old system I picked up outside in my street 😉