[Jason Oldfield]

Heck, do it for 5 years to get people hooked, and then start charging at the gate again! If you're getting huge crowds, you can charge a menial entry-fee once people are hooked (I'm talking like $5/each or less), and they'll still pay.

It's the whole razorblade / razor marketing campaign (or the give the crack away to people to get them addicted before you start charging them thing if you want to be non-politically correct).