Coca-Cola and Pepsi make unreasonable amounts of money on a product that they produce for almost no cost at all. About 40% of their revenues is spent on marketing.
However, there’s serious competition on the horizon. OpenCola, like Linux, is licensed under the GNU General Public License. Based on the recepies of OpenCola, you’re free to make, sell and distribute your own coke and you’re free to improve it also, as long as you keep the source ‘open’.