There are several possible explanations to this marketing strategy:
#1 - The makers of Monster do think people who drink this energy supplement are not very bright.
#2 - The price of cardboard has sky-rocketed and I have not heard about it.
#3 - This is an example of new math gone mad.
#4 - The guy in the company who did the pricing strategy is a graduate of some university where math has been through the self esteem movement and answers in arithmetic are "whatever you feel they should be."
#5 - One of the hidden characteristics of Monster is that while your energy is restored your reasoning is wiped out.