It is never cheaper to feed your family junk than it is to prepare real food. An onion, a tin of chopped tomatoes and enough pasta to feed four can be had from Tesco for a total of 48 pence. Go mad and buy some garlic and some mixed herbs - you'll still feed four for under a quid. What's more you can cook it in two pans on one ring in 20 minutes.
Now what junk food joint can do that?
Sorry, but I am judgemental on this. There is seldom an excuse for feeding your family crap, and anyone who regularly feeds their family at junk food restaurants is guilty of abuse in my book.