The price is always-or at least often--lower when you buy in bulk, or larger quantities, like my experience with the sweet corn.
I don't use much milk myself. I rarely eat any kind of cereal for breakfast, and I never drink the stuff--tastes nauseatingly awful to me unless it has chocolate in it. So pretty much I just use enough per day to whiten one cup of coffee at breakfast on weekdays, more on weekends. Occasionally I will use it in cooking (homemade mashed potatoes), but that's rare.
I don't understand how the price discriminates against cows. A cow will give however much she's going to give, regardless of whether the dairy bottles it by the gallon or by the quart.
Of course I've never been a parent, but I would have thought a mother, or any parent, with more than one child would run out of a gallon of milk before any of it would spoil, but perhaps that varies from family to family.
I'd rather pay more for a quart and use it up before it spoils than pay less for a gallon and throw half of it away.