How does food waste reduction functionally contribute to the concept of the cheapest food?

By preventing the money spent on spoiled food (like sprouted potatoes) from being wasted entirely

The true measure of the cheapest food moves beyond the initial sticker price to consider the entire outlay of money spent on consumables. When food is purchased but subsequently spoils—for example, potatoes sprouting or herbs going bad—the capital invested in those items is effectively lost, meaning the final cost of the food actually eaten becomes inflated. Learning proper storage techniques to prevent spoilage, or mastering simple preservation methods like drying herbs, ensures that the initial monetary investment translates directly into consumed calories or nutrients. Therefore, waste reduction is a powerful, indirect method of lowering the effective cost of the food that successfully makes it into the diet.