My experience was the opposite. We were dirt poor and had home cooked meals all the time, it was way cheaper than fast food or microwaveable meals.

Buy 10 kg of rice, a bag of beans and some frozen veggies for under $20, cook it all at once in a big pot. You've got 10 meals for under $20 and maybe an hours time.

Put it in the fridge/freezer and you've got healthy meals for a week that cost $0.50 each.

Not sure how a single $10 meal at fast food could be considered "a cheaper alternative".