That big mac is at the end of a literally global supply chain. The cost of the tires on the car of the fry cook and the number of temperature sensors one can afford to put in the reefer ship that gets the tomatoes from Argintina all have an impact on the overhead of a big mac. And this is in addition to all the direct process improvements others have mentioned. Heck, the internet has opened up a whole new world of operational efficiency for the farmer that grows the grain that feeds the cattle. He can buy parts for his machines or compare spec sheets for fertilizers from his iphone while sitting in the cab of his tractor that almost drives itself. In 2001 he had to thumb through a catalog or call someone.