This isn't my experience--I've worked with hundreds of developers who do open source, and only a handful were paid in any way. I don't exactly look deeply into the finances of every open source project, but my own open source projects, I've paid to run. Now, I'm aware that my experience is anecdotal, so I'm not going to confidently say that you're wrong, but I'll say that the best evidence I have (which isn't very good) doesn't match your claim. If you want to persuade me, you'll have to provide better evidence than what I already have.