Is Burning Man fun? I got the rather cynical impression that it's mostly very well off tech people and even better off finance/political people.

You're not far off.

Burning Man is like Coachella, SxSW, and San Francisco, itself.

It used to be cool, and interesting, and counter-culture.

But then it got overrun by tech people and grifters and assorted wannabes who think they can buy their way to coolness, when that's something that can only come from within.