Nostalgia and natural rarity. If it weren't for emulators, I'd wager that old Nintendo systems would be the rage right now.
Stashing a mint NES back in 93 with the hopes of making fat stacks today would have been a folly because of how people are valuing the whole thing(they value the game/experience, not the console/object).
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.eb...
Yes, the ROM can be had for free and the experience of playing the game is identical. No, a collector doesn’t care.
Maybe I'm just being pedantic?
The casual nostalgics are happy with emulators, hence the systems not being expensive. Still enough SNESes out there to placate the the small number of people that want the original.
LEGO would certainly fit the bill
On the plus side, I had a lot of fun showing off & playing with my dad's "investment" as a teenager.
As an aside, his dad was for the most part a pretty smart guy, he had a PhD in Physics. He just got caught up in the hype and made a bizarre financial decision after reading articles on the projected value of baseball cards in the future.