My answer is, yes and no.
Blueberries are expensive. Bananas are not.
Steak is expensive. Eggs are not. At two eggs per serving, they put the protein in your meal for about twenty cents.
Name brand ready-made fancy granola cereal is expensive. Oatmeal is not.
Boneless, skinless chicken breasts are expensive. A whole chicken costs less per pound and is far more versatile.
Brown rice is filling and nutritious and inexpensive.
Lentils cook quickly compared to other beans, are high in protein, and are inexpensive.
Shelled walnuts are expensive. Sunflower kernels cost less and have similar nutritional value.
Ready-cut carrots are expensive. Whole carrots are not. Cabbage, potatoes, and onions are inexpensive and nutritious.