If you spend your own money on yourself, you tend to be very careful both how much you spend and how it is spent;
but if you spend your money on someone else you are still very concerned about how much is spent, but somewhat less concerned about how it is spent;
but if you spend someone else’s money on yourself, you are not much concerned about how much is spent but you are concerned about how it is spent;
but if you spend someone else’s money on someone else, you neither are very concerned about how much is spent or how it is spent.
Milton Friedman, 31 de Julho 1912 – 16 de Novembro 2006