It is impossible for man's happiness to consist in wealth. For wealth is twofold, as the Philosopher says (Polit. i, 3), viz. natural and artificial. Natural wealth is that which serves man as a remedy for his natural wants: such as food, drink, clothing, cars, dwellings, and such like, while artificial wealth is that which is not a direct help to nature, as money, but is invented by the art of man, for the convenience of exchange, and as a measure of things salable.
Now it is evident that man's happiness cannot consist in natural wealth. For wealth of this kind is sought for the sake of something else, viz. as a support of human nature: consequently it cannot be man's last end, rather is it ordained to manas to its end. Wherefore in the order of nature, all such things are below man, and made for him, according to Psalm 8:8: "Thou hast subjected all things under his feet."
And as to artificial wealth, it is not sought save for the sake of natural wealth; since man would not seek it except because, by its means, he procures for himself the necessaries of life. Consequently much less can it be considered in the light of the last end. Therefore it is impossible for happiness, which is the last end of man, to consist in wealth.
The desire for natural riches is not infinite: because they suffice for nature in a certain measure. But the desire for artificial wealth is infinite, for it is the servant of disordered concupiscence, which is not curbed, as the Philosopher makes clear (Polit. i, 3). Yet this desire for wealth is infinite otherwise than the desire for the sovereign good. For the more perfectly the sovereign good is possessed, the more it is loved, and other things despised: because the more we possess it, the more we know it.
Hence it is written (Sirach 24:29): "They that eat me shall yet hunger." Whereas in the desire for wealth and for whatsoever temporal goods, the contrary is the case: for when we already possess them, we despise them, and seek others: which is the sense of Our Lord's words (John 4:13): "Whosoever drinketh of this water," by which temporal goods are signified, "shall thirst again."
The reason of this is that we realize more their insufficiency when we possess them: and this very fact shows that they are imperfect, and the sovereign good does not consist therein.
ST I-II, Q2. A1.