[pessimizer]

The difference is whether the market is ultimately driven by people who want to own things or who want to flip things. It's not black and white, but I bet <1% of people who bought Beanie Babies wanted to own Beanie Babies, and at least 50% of people who buy collectible Pokémon cards (or baseball cards, or comic books) actually want to own them. For the people who actually like Beanie Babies, the market for them isn't terrible, it's wonderful. They can afford everything they want.

A market of flippers (like Beanie Babies) has to terminate at bagholders. While you can also lose your shirt in a collectors' market, it's because they're driven by the tastes and disposable income of those top-level collectors. They tend to shift from area to area based on particular books, articles, or even influential threads on message boards, and those markets move as a whole with wealth inequality and against interest rates, like fine art.