And Coca-Cola has an ingredient benefit - the fact they have a license to put coca into the drinks is completely unique in the industry AFAIK. It might be troublesome for a competitor to get that same license.
Technically, Coca-Cola puts in a coca leaf extract that is produced by Stepan Company. They are the ones who have the only license to import coca leaves in the US and they use them to make medical cocaine. The extract they sell to Coca-Cola comes after all the good stuff is gone. Coca-Cola never touches the leaves.