Believe me when I say there many different reasons for different prices when the station owner has to buy it because of;
1. The station volume
2. Brand
3. Freight distance
4. Location—overhead cost
5. Cost of local labor
Also right now most Station volumes are down. I would bet 25 to 50%.
Most overhead stays the same—utilities,taxes,mortgage,insurance, etc.
It is also the only business that HAS to post the price on the street where everyone can see it.
Also no one complains when 1 store sells milk for $4 a gallon and the one down the street has milk at $2.69 gallon.