I can see where the store brand varieties of items such as milk, butter and such could be considered commodities. But the premium items, like Fairlife, which has went through additional processing, considerably different than regular milk, really isn't.
It seems that it is unrealistic to expect specialty varieties of food items to be priced similar to the basic varieties. Butter is a perfect example, with grass fed varieties vs store brands. Organic vs regular produce. Store brand yogurts that can be had 3/$1 vs something like Chobani, which clearly has premium ingredients and processing, and costs 4x as much. And now, milk.