It doesn’t take a billionaire,
but it certainly doesn’t hurt. A couple million can work, or half a million if someone is crazy.
Your point still stands though.
You can raise capital so easily with any traction (seriously, if you have any credible paying customers at all YC will take you and that unlocks funding from everyone else). The cost of health insurance is negligible compared to the astronomical salaries of software developers.
And billionaires are much more scarce outside of US (and those who exist have better chances investing in other fields).
That's why SV salaries for developers are so crazy.