A fully autonomous AI agent is programmed to go on to the internet and create cryptocurrency wallets, then create crypto currencies, then endlessly create millions of similar versions of itself that want to trade that crypto.

Now let's assume all these AIs are programmed to try to indefinitely increase the value of their crypto, something they accomplish in similar ways humans do—by promotion and then trading their cryptos for higher values. Additionally, the autonomous AIs open their crypto to be traded with humans, creating a functioning market on the blockchain for all.