My first Burn was about $1,000-1,200, on the absolute cheap (rideshare from 4 states away, free tent, shared shade). Including the ticket.
I spend . . . more than that, now (probably twice that) and like Junglesmacks, I don't really like to think about it.
I just sock away as much as I can. I also re-use almost everything from year to year, and buy food not specifically designed for camping that I will actually want to eat later on, when (as usual) I only eat 20% of it at the actual event.
Two local friends of mine were guessing at dinner the other day that they spend about $3,000 apiece.
It will always cost hundreds more than you expect. Especially your first time. If you shop early and bargain hunt, hit sales, use coupons, go to discount stores for certain things, buy gently used equipment from friends and relatives, etc, you can get the most out of your money. And if you have relatives who buy you presents around the holidays, put camping stuff on your Wish List.
. . . With regards to the ticket price in particular, I believe it's Doc Pyro who is fond of saying: you're not paying $390 to get into a party . . . you're paying $1 to get into 390 parties.