First, personal preferences are subjective. It is close to impossible to represent them as numbers. Can I make a statement like Ram is 1.5 times as happy with two mangoes as Shyam is with three apples? These can serve as indicative ideas in economics textbooks, but cannot be the basis of serious economic policy making. Personal preferences should not be confused with, say, choices between vanilla and strawberry flavours of ice cream. Here, they are about what a poor man faces when he has an incremental Rs 10 and he has to make a subjective choice between spending it on healthcare for his ailing mother, or for food for his hungry daughter, or a combination of the two. With every incremental Rs 10, the same question needs to be answered by him again, until he can begin to think of repairing the leaking roof of his hut.