It's free for spectators.
There's usually some pretty nice rides there. And you get behind the scenes if you like to see that sort of thing. One year there was a team busy working on S7s. And if you don't get to drool on an S7 or Ford GT often enough, there's usually one of each around.
I haven't done a lot of shows in recent years, but figured I'd at least have a place to park and walk around. Last show I did was Knott's, but I'm also thinking about one of the SVTOA shows coming up... I just try not to get up too early on weekends.