Plus, if you try to sell the monster at a higher cost than coke, what would stop someone from dumping the coke, and refilling with monster? Paying the lower innitial price, and now getting refills.

People have been doing that for years with buying water, and then filling it with fountain drinks.

I suppose you could counter it the same way that some stores handled the soda refill issue. Have the energy drink refills behind the counter, where only employees can refill it. Have a special cup so employees can tell which customers actually bought an energy drink. Also gives employees a chance to intervene if someone tries to get too much and kill themselves (like with the Panera Bread lemonade/