Why does a salad cost more than a Big Mac?

Answer: The billions of dollars of federal subsidies included in the Farm Bill. That's right, the ingredients of that special sauce are making somebody pretty wealthy. From the Physicians Committee for responsible Medicine (PCRM):

The Farm Bill, a massive piece of federal legislation making its way through Congress, governs what children are fed in schools and what food assistance programs can distribute to recipients. The bill provides billions of dollars in subsidies, much of which goes to huge agribusinesses producing feed crops, such as corn and soy, which are then fed to animals. By funding these crops, the government supports the production of meat and dairy products—the same products that contribute to our growing rates of obesity and chronic disease. Fruit and vegetable farmers, on the other hand, receive less than 1 percent of government subsidies.

The government also purchases surplus foods like cheese, milk, pork, and beef for distribution to food assistance programs—including school lunches. The government is not required to purchase nutritious foods.

Read more here.

The irony, of course, is that the original Farm Bill was created to aid small, family farmers the help they needed to compete. But most the assistance in the 2007 Farm Bill will go to a very small percentage of American farmers. Efforts to reform the Farm Bill were defeated, and yesterday the bill was approved by the Senate Agriculture Committee.

In a statement from OXFAM:

While Oxfam welcomes critical new investments in nutrition, conservation and renewable energy, the Farm Bill approved by the Senate Agriculture Committee today failed to reform our unfair and broken system of commodity subsidies that undercut farmers and rural economies at home and abroad. Unless the rest of the Senate intervenes, our taxpayer dollars will continue to encourage excess production, reduce world market prices and undermine the livelihoods of millions of small farmers around the world.