First principles: Buy basic raw foods cheap (chicken, pork, tough cuts of beef for slow cooking, vegetables, fruit, and starches) and cook at home. Discount stores and weekly food ads are your friends. Not only cheap but far healthier than heavily processed sugar infused crap. The main problem, of course, is that all requires forethought, intelligence, and a will to work shopping and cooking. None of those characteristics come to mind with today’s “poor”.
Nailed it!