Tech billionaire Bill Gates has dismissed NFTs as “100 percent based on greater fool theory” — the financial concept that even overpriced assets can make money as long as you find a bigger idiot to sell them to.

Speaking at an event on climate change hosted by TechCrunch, Gates said he preferred investing in assets with tangible outputs, like farms or factories, “or a company where they make products,” and that he held no position in cryptocurrencies or NFTs. “I’m not involved in that. I’m not long or short in any of those things,” said Gates, suggesting that he was also suspicious of assets designed to “avoid taxation or any sort of government rules.”

“Obviously, expensive digital images of monkeys are going to improve the world immensely,” quipped Gates, referring to the flagship NFT project, Bored Ape Yacht Club.

It’s not the first time Gates has expressed skepticism about cryptocurrencies. In an interview from February 2021, he worried about the dangers of regular investors buying into Bitcoin, especially when the cryptocurrency’s value was so volatile and could be tanked on the basis of a tweet from a prominent investor, like Elon Musk.

“I do think people get bought into these manias who may not have as much money to spare,” said Gates in 2021. “My general thought would be that if you have less money than Elon, you should probably watch out.”

Gates’ warnings about volatility were spot on. When he was speaking in 2021, Bitcoin was surging in price and would reach a height of $63,000 in April that year. It would then slump dramatically, before rising again to an all-time high of more than $64,000 last November.

Since then, the price of Bitcoin has crashed once again, and at the time of writing is trading just above $20,000. This dramatic fall is part of a wider set of convulsions rocking the crypto world, after the collapse of so-called “stablecoin” Terra in May and the ongoing failure of crypto lending platform Celsius.

Similarly, prices for NFTs have also fallen sharply. Some of the biggest projects, like the aforementioned Bored Ape Yacht Club, have more than halved in value. At the same time, trading volume has increased, as buyers seek to snap up digital assets at rock-bottom prices. Like Gates, perhaps, they may be subscribers to the greater-fool theory of NFTs — confident that there are more idiots out there, if they can only find them.