It's certainly addictive to some degree, if only for the fact...

It's certainly addictive to some degree, if only for the fact that it is a food that contains sugar and caffeine - both of which are somewhat addictive. I'd put it somewhere between alcohol and water in terms of addictiveness.

Main point I was driving at, though, is that Pepsi or generic cola is no more a substitute for Coca Cola than generic tomato sauce is for Heinz ketchup. Most people who are used to using Heinz's brand of ketchup will be able to taste the difference if you give them a different ketchup brand. Likewise with Coca Cola. So from that loyalty, both of these brands can justify charging a small premium for their products.