You are doing a good turn by helping mom and dad out with the meals. Finding time to cook can be the hardest part of putting good food on the table under a budget. Especially in urban areas, time to cook those meals is valuable too.
I'm not criticizing terps if his food budget seems high to me. Sometimes people trade off cost and convenience for time, especially when both parents are working, are making good money and don't keep an eye on the food budget. The rat race is getting more and more intense and people have to make trade-offs where they must. On the other hand, his insistence that feeding a family of four well for less than 30 bucks a day is unthinkable seems a bit stretched, even in these busy times.