True. I’ve heard that proprietary blend also adds to cost, because it apparently is more expensive to refine that particular blend of gasoline.
Hubby had a refinery in his station boundaries that he used to inspect. He was a Captain for our county fire department. He said he used to watch all brands of trucks, Mobil, Chevron, etc., pull thru to fill up and then the refinery would just add whatever additives the brand called for.