How about, say, Pokemon cards? Lots of people buy them with an expectation of profit, which relies on the efforts of The Pokemon Company (among others) to continue to grow the player base.
They very well could be. I'm knowledgeable enough to answer.
I also wonder how does it work with one-of-a-kind collectibles, such as old letters written by famous people, paintings, rare/unique coins, ..., and NFTs.
