High-calorie, low-cost processed foods, like those Ben Affleck may be eating this week as part of the “Live Below the Line” campaign, cost less at the check-out counter because they are cheaper to produce, transport and store than fruits and veggies.

Plus, Uncle Sam gives that grub a dose of financial fertilizer.

Affleck, along with other celebrities, including Hugh Jackman and Tom Hiddleston, have pledged to eat on just $1.50 per day for one week — to draw attention to poverty. Here’s why living on so little often leads to a poor diet in the United States.

VIDEO: Stop Eating Food: The Soylent Experiment

Even if an American only buys produce at the farmers market, they still pay for processed foods with their taxes. The United States government pays farmers for growing some crops like corn and wheat, but doesn’t pay as much (or at all) for others. The lack of subsidies for some crops, like lettuce and broccoli, artificially raises their market cost compared to grains and oilseeds, noted the Atlantic.

The Farm Bill decides which farmers get the funds. The Senate Agricultural Committee  Farm Bill announced plans to start a mark up of the bill on May 15, reported Ag Week.

ANALYSIS: Sugarcane Cools Climate, Heats Up Tax Debate

Subsidies aren’t the only economic advantage of processed foods. Highly-processed, preservative-laden foods’ ingredients mostly come from vast, mechanized farms, densely populated livestock operations or automated factories.

Industrial-scale operations then combine those raw materials and package and distribute them. Since fewer workers are required to create food this way, the cost of production for a just-add-water dinner stays lower than the cost of an organic apple.

ANALYSIS: Organic Farming Helps Vets Recover From War

Transport of processed foods required fewer precautions, which also makes them cheaper. A simple experiment can prove this point. First, place a few ripe strawberries in a backpack along with a box of mac ‘n’ cheese. Then carry that bag around with you all day. In the evening, you will have probably have an unappetizing smear of free-range strawberry jam and a perfectly edible box of mac ‘n’ cheese.

The 20-letter long preservatives in many highly-processed foods makes them cheaper to warehouse as well. A banana will have disintegrated into a brown mush long before a snack cake even goes stale.

ANALYSIS: Organic Farming Increases Soil Quality

In the case of whole grain versus white bread, chemistry also influences cost.

Grains, like corn or wheat, are seeds. They contain the germ, the biological bit that would have eventually matured into a sprout. The germ will rot quickly because it contains oils and a mixture of other chemicals.

Milled flour can be stored longer and less expensively than whole grain because the germ has been stripped away along with the husk, or bran. However, milling also removes more than half of wheat’s B vitamins, 90 percent of its vitamin E and most of its fiber, according to the Harvard School of Public Health.

IMAGES: Macaroni and cheese (Antilived, Wikimedia Commons)