"Isn't much cheaper" is still way cheaper than fast food. Just changing your diet to something with less sugar, less fat, less saturated fat, less salt and a more balanced amount of carbohydrates and proteins is going to do wonders in bare months. Even if you keep your calorie intake a constant (which, with healthy food, it means you're gonna eat a fuck ton more).
Healthy food is cheaper not for the price itself, but for the net long term benefit. Less chances of diabetes, cancer, cardiovascular diseases, while improved vitality, energy and fitness levels.
Should healthy food be cheaper? Yes, it definitely should. Should the estate subsidize or cut taxes on raw food and basic items? Hell yeah it should. Nonetheless, while we still fight and ask for that, eating healthy at home is still cheaper than buying in unhealthy fast food chains.
I don't know your family composition, but even here in Europe, 30€ for a quick meal for 4 is fucking cheap. Like, under the poverty-line cheap.