I've never understood that point. Home cooked meals are cheaper than fast food or ready made meals or just junk food.

Buckwheat, rice, pasta, potatoes, oats can be bought in bulk and are one of the cheapest components. Unflavored lean meats are rather cheap as well, cheaper than candy bars per KG/lbs. Buying those on a sale, separating packages out for portions and throwing in the freezer.

Greens (cucumber, paprika, tomatoes) are the most expensive component, but even those are cheaper than junk food.

Only argument might be that ready made meals are slightly cheaper if comparing single item price not per KG/lbs, but most components for home cooking are for multiple meals.