This is BS because healthy food is cheaper than unhealthy. If you buy bulk meat, potatoes, vegetables and make a huge stew that serves 4 people a meal for the next four meals you can do so for under $10. Try doing that for ready meals, or McDonalds, or other unhealthy sources.
It's true. People make the "junk food cheaper" arguement based on calorie per dollar anaysis... which are fatally flawed.
If anyone really can't understand why, just eat a Candy bar in comparison to an Apple.
The Apple is more filling AND has less calories.