Eddie,
The Breweries sell it to the Supermarkets for a profit.
The supermarkets sell it at a loss.
So the breweries are happy, they are selling large volume at a profit.
The customer is happy, because the supermarket is subsidising the price.
The supermarkets make money on the other stuff you buy while you are getting your beer, so the supermarkets are happy.
The milk situation is totally different. You tax money is given to farmers and the result is over supply. Supermarkets buy the milk cheap. The customer is the loser, because they are being hoodwinked. They think they are buying cheap milk, but they are not factoring in the tax they pay beforehand that goes to the farmer.