"That being said, the very nature of the event involves spending thousands of dollars to live in the desert for a week. So the audience is obviously mostly people who have the money to do so."

It depends what standard you need, but I have been to (way smaller) desert gatherings where people with no money came. (Not as remote, though, possible to walk there with a tent). But as far as I know, the main thing you need for burning man is a van and water, or know someone who has one.

I'm under the impression that paying for tickets is not exactly frowned on but isn't the respectable path either. The alternative being to do something awesome at a regional burn and get recruited by an established camp, which comes with free tickets.

I have no idea how common this is. I just know somebody offered free tickets for me and my crew if I joined his camp with my contraption at the big burn.

I like the idea, decommodification being one of the principles and all, but I didn't go because I didn't have time to fix some issues that I deemed critical.