I spent a bajillion bucks importing Japanese-language yaoi and shonen-ai manga when it wasn’t available in the US. Now nobody wants it.
I bought a gaming book back when I was around 12 that quickly went out of print, and -then- gained a following. About 10-15 years later, I found out that said followers were rampant ebay watchers, and said book, bought for about ten bucks, would go for upwards of a hundred. I toyed with the idea of selling it, but decided I’d rather keep it, just in case I wanted to use it some day.
About 2 years later, the author of said book, after a long legal wrangle, made the entire thing available online for free to anyone who wanted it. Oddly, I was more happy with the whole arangement than bummed about it.
(And yes, I realize it only depreciated by ten bucks from the original value, but it appreciated first.)
(Is appreciated the right word there?)
I still have, but haven’t used in an age, a very early laptop, probably one of the first. It’s a Toshiba 8086, dual 3.5" floppy, no hard drive, that went for around $1300 new. I’d imagine I could probably get $15 from a dead tech collector now.
An unused airline ticket from Paris to Prague that I paid about $200 and is now worth exactly zero.
I have a working Olympus digital camera that I paid $600 for, circa 1997. Those 2.1 megapixels were about the top of the line at that time. Got great results, used them to help create a website.
Now of course you can get a 10 megapixel digital camera for under $100. I suspect the resale value of my Olympus is somewhat lower.