This isn’t even true. A cart of rice, beans, sweet potatoes, and frozen/canned vegetables is always going to be cheaper than pretty much any other assortment of foods.

The issue is that many people live in rural food deserts, which means that they don’t live near much of anything other than fast food restaurants or stores like Dollar General. Rural environments (in the U.S. anyways) practically necessitate a sedentary lifestyle, as there’s no way to walk to where you need to go. And the food options are utterly lacking, unless you’re able to regularly make the long drive required to stock up at the closest town that has something like a Walmart.