Here's one of the things that doesn't get talked about very much in the US. The average household spends roughly 9% of household income on food. This compares to 11% in the United Kingdom, 16% in France, 17% in Japan, 27% in South Africa and 53% in India. (These are numbers form 2004).
The US is able to do this largely because of the issues that onesnowyowl has raised around the Farm Bill and subsidies. The subsidies have produced a glut of produce such as corn and soy beans. This is not the corn of "corn on the cob" this is industrial corn and soy beans that are used as a supply of food for vast, industrialized cattle feedlots and the building blocks of processed foods.
I have read somewhere that if you need 1500 calories a day to survive and you were to buy 1500 calories of fresh food vs. 1500 of processed foods you would spend approximately $1.50 on the processed and $4.00 on the fresh. (caveat... I am doing this from memory so the numbers might be off a bit, the point is the divide between the expense of fresh vs. processed). Processed foods are less healthy.
The Farm Bill is about creating large quantities of cheap food and the US has been very successful at doing just this since the early 70s when the Nixon Administration made this a priority and altered the existing policy.
One thing of note: I wonder how the drive to use the surplus corn for ethanol will effect food prices. Wait...
Secret report: biofuel caused food crisis. It looks like it already has.