I don't know about NASCAR, but have been a vendor at the Sturgis Motorcycle rally for over 20 years. Here, you get what you pay for. I pay top dollar to be in one of the most popular campgrounds/music venues of the rally, and it is worth it. I know many people who tried to save a buck on the vendor fees and took an inferior space. It usually comes back to bite them in the butt. Most never try it again after taking a loss.
You need to look at the options you have during the event and see how busy they are. Is there anyone around in the campground during the races? Do they come and go? If so, they can bring food in with them or eat while they are out. Don't forget that most motorhomes have full kitchens, so how many of the attendees will pay top dollar for a dog?
When we first started doing the rally, everyone showed up on their bikes and didn't have any way to cook, so we did great. Now with over 7000 RV sites and everyone with a kitchen and microwave, our business has changed quite a bit. We don't do much at supper time since people tend to eat at their camper or in town before they come back for the concerts. Our big time is during and after the concerts when the customers don't want to walk back to the camper, but need a snack.
Another good indicator of how good a venue is, is how easy it is to get a space there. Good venues have waiting lists that can take years (or big bucks) to get into. If you can easily get into a venue, it's probably because the former vendors lost their shorts there and don't want to come back, or the payoff isn't worth all of the trouble.
Other things to look at are if the required you to be open certian hours and will you do enough business during those hours to justify the labor? What is povided? Electricity, water, garbage removal, parking for your vehicles, a space to camp, wrist bands or other access for all of your employees, set up and tear down time, etc. We changed locations last year to try out a new venue and different menu (used to do pizza, sold out of that business and went into indian tacos and hot dogs), and even though we were in the same campground and were dealing with the same people, the rules changed with the venue change. We used to have a hook up to a sewer, but the new space didn't have a sewer and we were now responsible for getting rid of our waste water. Since we were not in the concert arena any more, our employees no longer got wrist bands to get into see the concerts (something that was a great selling point when trying to get help to work the event).
Another thing to look at is access to your booth during the event. What happens if you run low on supplies, can you get out to get more? Some events limit the times when you can make or recieve deliveries.
Are you required to buy certian items from them or their approved suppliers (usually ice, drinks, etc.)? Sone venues require you to buy from them or their suppliers at a large mark up.
Will you have an exclusive on the items that you sell, and do they limit the number of venors, or take everyone that will pay a fee?
And where in the venue will you be set up? We once worked an event and were put next to the outhouses! Not a great place to sell food. You want good visibality and access to the crowd, not a space in the back forty.
Hope this helps.
PS: I'm a fellow JarHead, Semper Fi!