The risk is absolutely real, and varies immensely, as does its significance.
Consider the risks of VC backed initiatives, which far more often than not, return less than market salary to entrepreneurs, and less than the S&P 500 to capitalists.
For a shot at the jackpot, entrepreneurs are risking substandard salaries, and capitalists substandard returns.
You could argue that the capitalist’s risk is more significant than the entrepreneur’s. Even in failure, a VC initiative can afford the entrepreneur greater networking and professional experience than other roles, which increases their future earning potential and offsets their risk of substandard salary.
Hard to say the same for the capitalist, who is also, of course, risking a far greater amount of currency than anyone else.
But a risk’s significance is not determined by the amount wagered; it is determined by the consequences of losing the wager. As well as the consequences of participation, or lack thereof.
Median American lifetime earnings are somewhere between one and two million dollars; let’s say an entire life costs two million. A capitalist capable of investing a billion dollars could risk an entire lifetime’s money on a venture every other month, for eighty years, cradle to grave, and if they suffered complete losses every time, they’d still die with enough money for 1600 years of life in a wealthy nation.
The sum risked is immense. But the consequences of losing it are null.
It is, of course, more nuanced than that. Many businesses are funded by people with far less than a billion dollars, and many of them fail. There's also 3,000 billionaires, and an overwhelming majority of human lives that cost far less than American's.