In my humble opinion. Chalav Yisroel milk is overpriced and due to poor packaging (you can easily feel the difference between a bottle of CY and any stam milk) does not last very long and spoils rather quickly.
Again, this is my opinion, and I am not stating this as fact. CY companies are in business for themselves, not to provide yidden with CY milk. If they cared about the average consumer they would sell their milk in GALLON containers. Simple econimics says that because they can not charge 2x a half gallon for a gallon bottle, they make more per gallon this way. Until a CY company is willing to answer WHY they wont sell gallon size bottles, I will believe it is due to their greed. I have written letters to these comapnies and have not been given the courtesy of a response.