Interesting.. I am in NJ and the highest price I saw for premium is $ 3.
But this is what happened to me at one of the local gas station few weeks ago. I put $ 40 with Plus @ about $ 2.70. So, it was roughly 14.8 gallon. I know my car good enough that this was correct amount (also, the pump said the 14.8 gallon). When I received the receipt, the receipt somehow said 13.8 gallon of Premium @ $ 2.90 and total was $ 40. So, the total was $ 40 no matter what, but it was only the receipt that showing wrong detail. I, of course, didn't care as I know 14.8 gallon was put.
What happen was that Credit Card machine is set up this way: The machine and pump are not linked, and you have to manually enter the total amount. And then you enter what grade it was, then it calculates gallon automatically and prints on receipt. Attendant didn't care much about the grade and just pressed "Premium" instead of "Plus". Therefore, it printed the receipt showing the total amount of $ 40 with Premium @ $ 2.90 and automatically calculated volume of 13.8.
It probably was what happened to you by looking at fairly higher per gallon price on receipt. They were lazy and not updated the price. So, in their machine, the price is set up @ $ 3.419 for Super. Attendant enters $ 50.02 and chose Super. Machine prints the receipt with outdated price for Super and wrong volume.
Of course just my guess 🙂