For drinks that get free refills the initial sale means more than the refills. It literally cost 1c to provide the drink and you sold it for $3.00 (that's the 300% margin). Who cares if you spend another 1c to provide a free refill if that would be the difference in the customers mind on whether they should buy the drink initially or just have water or OJ (something that has negative margin, or a very low margin).