Correct. Moreover, you actually need to count mostly only the protein intake, because when your food does not have enough calories that becomes obvious, becaus

Correct. Moreover, you actually need to count mostly only the protein intake, because when your food does not have enough calories that becomes obvious, because you lose weight. Obtaining enough calories for a day requires spending only a small fraction of a dollar per day, for buying enough wheat flour or corn flour. When you attempt to minimize the cost of food, most of the money will go for ensuring an adequate amount of protein, with an acceptable amino acid profile, and also for ensuring adequate amounts of essential fatty acids, vitamins and minerals. Ensuring enough calories is by far the easiest part.