You are assuming everyone who tailgates (or not going to tailgate) has a ticket to the game.
The OP stated he had tickets.
You said above that they'll stop charging 3 hours before the game. That's more than enough time for someone to arrive to campus and then go to the game. Just not enough time to make it worthwhile to tailgate (or set-up tailgating, rather). People who aren't going to make the effort under this situation, I highly doubt they would have gone to the game anyway.
Huh? All I'm saying is that people who still want to go to the game but not tailgate will show up late.
We host a semi-large group. Most have tickets, but since people are coming from all over with different schedules there will be a number of them that will just show up 2 hours before the game, stop by for 30 minutes then head into the stadium. Previously, they would have just shown up, parked 50 feet from our tailgate.
I don't see an individual in our group paying $40 to do so.