Dexter makes the association early on in both his life and the story that wealth and happiness go together. His experiences on the golf course proves this. Recall the pride he felt about being in a foursome with some of the very same people for whom he used to caddy when he is an emerging businessman. There is a certain sense of pride and elation felt because he believes that being wealthy and being happy are one in the same. The fact that he leaves Irene and decides to pursue Judy reflects this. Due to the fact that she represents wealth, Dexter is able to dismiss many of her bad habits. In the end, when he hears of her decrepit and broken condition, it becomes the ultimate reminder that wealth and happiness are two separate things. Dexter's weeping at the end might be for this realization as much as it is for the death of his own dreams.
Dexter believes the wealthy are successful and happy people. In fact, when his father offers to pay his way to the state University, he refuses and chooses instead to pay his own way to a more prestigious school because in his mind he wants to be wealthy not just be associated with wealth.
Dexter's association of wealth and success stems, in part, from his experiences as a golf caddie at the country club. In that role he is often associated with wealth even if he is never wealthy himself. In fact, it is his encounter with a rather pretentious young Judy Jones on the golf course that drives him away from his caddie job because of her treatment of him.