One thing fascinating about that map: I live in KY and two weeks ago took a weekend trip to Knoxville Tennessee. As soon as we crossed the border, gas was ten cents less.
However, my FRS burns the most expensive blend. It was, in every station I stopped at (and I stopped at a LOT of stations) fifty cents more than regular. Meanwhile, it’s only twenty cents more where I get gas. IOW, premium cost twenty cents MORE in Tennessee.