Maybe the grocery store can't match it without taking a loss.I have posted elsewhere about the difference just in milk prices, that make no sense to me. Walmart charged $3.48 a gallon. Our local grocery chain charges $4.28. But this is the part I don't get. Our local grocery chain OWNS their dairy. That dairy bottles all the milk for our local Walmarts too. So unless I am missing something, our local grocery chain could match Walmarts price and still make money, but they choose NOT to.
Walmart is probably using milk as a loss leader - selling it at a loss so you come in for the cheap milk and leave with a cartfull of higher margin stuff.