Met-AL said:Regulation. At least where I live, there is regulation to keep places like Wal Mart from selling gas for just above the wholesale price to run competition out of business. Filling stations are required to price gasoline at least a certain amount above wholesale prices.
But even then, it's not the same everywhere. Try to get gas in New York City and then in who-knows-where Wyoming, and there will be a pretty substantial difference.