Without competition, you have the combination foodcourt/rest area found on eastern US toll highways, with overpriced, yuckky food. The McDonalds has higher prices at the toll rest areas than outside, and they don't take coupons.
Years ago, DFW had a single food service provider for the entire airport. There was overpriced, yuckky food, with no name brands and NO COKE. (Just Pepsi). After they got a bunch of different providers, I was able to get Popeyes and bring it onboard for lunch. With a coke.
It's like the old advice to public speakers, beware of analogies. Don't use one unless you've thoroughly analyzed it and you're sure it works.