The most interesting toy economy I’ve seen has been d2jsp and its “forum gold”. Forum gold is primarily used as a fiat currency for diablo 2 trading. It’s a janky digital currency on a janky forum from like 20ish years ago, that’s still alive today. You can technically buy the currency from the forum, but in practice few do that. Most people just trade items to bootstrap.

Having futzed with bartering in diablo (and non-fiat trading denominated in items of stable value), I quickly came to appreciate fiat currency. Being able to combine two “half trades” into an equivalent barter exchange is vastly easier.

At one point I was able to trade some of the forum gold I accumulated from diablo 2 for a “perfect IV foreign Ditto” for shiny pokemon breeding.