Anyone have a source for this oft claimed fact? Retail to spot spread is averaging $.50-$.70/gallon for 86 octane with $.20-$.30 added for each premium tier in

Anyone have a source for this oft claimed fact? Retail to spot spread is averaging $.50-$.70/gallon for 86 octane with $.20-$.30 added for each premium tier in PHX. Does adding detergent & transport eat up that much margin?