From what I understand, RBOB is the price of unleaded minus taxes, delivery, station profits, etc. So my question is - how can stations here in Phoenix be selling gas at 1.759 when RB is trading (today) at 1.33, when federal taxes are 18c and AZ state taxes are 19 for a total of 37c. And today's fuel was purchased at more than 1.33 a few weeks ago of course. Many midwestern states such as MO are even cheaper. They're transporting and selling at well under a dime a gallon and that seems very unlikely.
RBOB is the price in NY Harbor; there are hundreds of various rack prices across the nation that trade +/- NY RBOB. Each are subject to local supply/demand fundamentals and refinery economics.
Years ago I read that the normal Pump markup for regular unleaded is 2c/gallon and most pumps would lose money selling just regular unleaded. The markup on Super Unleaded tends to average 16c/gallon (wholesale Super Unleaded is only 2c/gallon more than regular unleaded). I doubt today's pump fuel was purchased a few weeks ago, unless the pump is a rarely used one in the countryside, in which case it probably has to charge more when prices are falling. Busy highway gas stations have tanker deliveries multiple times a week.