Milk

I bought milk tonight, and I noticed that skim milk was the cheapest. Each of the other types -- 1%, 2%, and whole -- was progressively more expensive. It hasn't always been this way. I remember that for some time, 2% was the cheapest; and no doubt whole milk was cheaper when they first started producing reduced-fat milk.

I would expect whole milk to be cheapest, simply because they don't have to process it beyond the pasteurization and homogenization that all milk goes through. Reduced-fat milk produces a useful byproduct, but it has to be replaced by more milk. Or does it? Milk is sold by volume, and I guess the fat is dissolved in the milk, in which case skim milk is lighter but just as bulky as whole milk. If so, skim milk would be the better bargain -- presuming the fat was worth more than the cost to extract it. It still might be a better bargain even if the fat took up space that had to be replaced by additional milk, but only if the fat was more valuable than the processing cost plus the cost of skim milk. I don't know how much fat is worth, but milk is pretty expensive, so I expect that fat dissolves in milk.