There's what I call the "cheap shoes fallacy" at play here.
When you buy cheap shoes, they break quickly, forcing you to buy another pair, ultimately costing more over time than if you had just bought good shoes to begin with.
The same applies to food. When you buy cheap food, it will nourish you only a little bit, forcing you to buy more of it, ultimately costing more over time than if you had just bought good food to begin with.
Cheap, industrial food contains the minimum amount of actual food to pass for grub, and is laden with artificial flavorings to fool your brain into thinking you're actually eating something, when you're not.