Greed is at the heart of the matter in McCarthy's story. One of the more intriguing aspects of the novel, when I first read it, was the question every reader asks themselves as the story unfolds: What would I do if I found a bag with $2 million in it next to a bunch of dead drug dealers?
I think most people consider themselves to be moral individuals, and that they would do the right thing the vast majority of the time. But $2 million is a serious moral test. So as we fear for the character Llewellyn Moss, we also empathize with his weak side almost immediately.
Greed is the reason the drug trafficking happens in the first place, the reason why Anton Chigurh is called, and the reason why Moss is ultimately killed for his efforts. So to see the central role greed has in the story, simply imagine what would have happened from the beginning if there had only been the bodies and the drugs, and there was no money at all, or Moss hadn't found it. The novel and the outcome would have been much different.