Why must Paul die in the end of the "Rocking-Horse Winner"?

I would also like to add that Paul is a sacrificial lamb in many ways.  In order to break this vicious cycle of greed and dissatisfaction, something dramatic needed to happen to give the characters a wake-up call as to what is really important in life.  The death of an innocent, young boy is shocking enough to institute change; if he had lived, the characters in the story would have surely continued in a static, self-destructive state embedded in greed and materialism.