Go to Oshkosh and try and buy a Coke... Pepsi yes and the opposition don't (or didn't) get a Guernsey
Don't know if it's still the case, but EAA negotiated with the service providers and agreed on the price that customers would be charged, whether it be food, drink etc. It was Coke who had the concession in my day, and price was one third of what you would pay at a football game. The EAA emphasis was on the family and affordability, not price gouging, and EAA ensured providers did not use it as a grand profit making exercise.