How does this even help?

Surely for the people who visit the site and do buy a ticket the revenue lost from them blocking ads would be basically insignificant compared to what they pay for their tickets. And obviously the people that visit the site while blocking ads and don't pay for a ticket won't be paying the surcharge.

I guess ultimately it helps by just bringing in extra revenue via a sneaky hidden charge that most people won't realize is there. But it doesn't really have anything to do with ad revenue.