I think the realistic take is to treat SaaS products like any other extremely skewed distribution, like income in sports.

Most people will barely make anything, some will be able to supplement their income, very few will be able to make a living. Even less will become "rich". For every product that blows up, there are thousands that will barely make anything.

But of course, it all depends on what your product does. If you make the millionth TODO / GenAI image editor / food calculator app and hope to make some money, good luck.