The price of a Big Mac medium meal is also a good index.
Your post reminds me of an experience I had a few years ago in the state of Delaware.
I went to do a McDonald’s in Delaware, ordered a filet o fish meal, and was astounded that the price was roughly half of what that cost me in California. I asked the cashier to double-check if he had charged me the right amount, because I wanted the meal deal, not just a fish sandwich. He assured me that the price I was being charged was for the meal deal.