Paper wealth unless you actually sell. I know several people who were paper decamillionaires in the dot-com boom and then their equity was worth literally zero a year later.

For that matter, that could easily happen to Anthropic millionaires. There's usually a 6-month lockup on employee sales after IPO. They are hoping the stock market (and specifically Anthropic stock) does not crash in the 6 months before they can sell, and this is far from a given in a rising interest rate environment with the potential for renewed hostilities against Iran. They also to be sensible enough to take profits off the table and diversify when they can, which not everybody is.