This is a great story and it shows the power of greed. More specifically the story explores the power of greed over people in that greed can tempt a man to do things that he would ordinarily not do. We see this very clearly in Kino, who finds a pearl, and puts his hopes in this pearl. To be sure, Kino's intentions are pure at first, since he only wants a better life for his family, but in the end he is willing to pay a very high price. He even kills a person who is tracking him down to get the pearl. In short, greed asks a question: "How far are you willing to do to get what you want?" The greedier a person is, the further a person is willing to go. In the end, greed will dehumanize a person, because a greedy person will go all the way, even if it means killing others to get what you want. See link for a religious view on greed.
In John Steinbeck's book "The Pearl" Kino a poor man in a village finds a pearl that is very valuable. He and his wife are so poor that they can not afford to have their child treated after he is bitten by a scorpion. Kino sees the pearl as the thing that will bring them great wealth and a better life. His wife tells him to throw it back into the sea. She fears what will happen to them if they keep it.
Kino keeps the pearl but right away someone destroys his property. He knows they want the pearl. He leaves with Kino to go with the pearl. While on the trip he realizes that he and his wife are being followed by trackers. Kino sneaks up on them. He knows they will kill him and his wife for the pearl. He hits one over the head and kills another. The third man runs away.
Kino is not the kind of man who wants to kill another human. The pearl has brought him and his wife nothing but grief. The greed of the others as well as Kino's own greed has made him capable of killing. In this manner the people have all become dehumanized. The trackers would kill Kino for the pearl and Kino has killed for the pearl.