Food isn't a ECON101 factory widget.

Farm subsidies are both the single most important national security policy a nation can have, and an incredibly inexpensive yet extremely effective insurance policy.

The Omnivore's Dilemma points out that the food economy doesn't even behave like the normal economy - supply is variable due to weather (bumper crop vs famine year) but demand is inelastic, people generally eat the same amount year-to-year. How do you grow your food business if people only eat so much? One method is to increase portion sizes.