Apples to Oranges?

Good:Transparency compares the cost per gallon of several different products.  The difference, of course, is that we don't use any of these other items by the gallon.  Tap water costs a lot less than $4/gallon, for example.  To do better, you would need to try to determine the utility/$ you get for each of these.  Coming up with a way to convert between the utility of a gallon of gas (20 miles traveled) and a gallon of coca-cola (1 all-night gaming session?) is the real trick.