>>16291886I think it's interesting because patrick bateman is punished by himself. He wants to fit into a specific group of people, and to accomplish that, he needs to sacrifice a lot of things (notably his peace of mind). He becomes agonized by envy and feeling left out.
Paul allen is the embodiment of just that. Allen is superior to Bateman (in bateman's eyes) and he's very, very agonized by that and decides to kill him.
The ending was also interesting because it just shows how hopeless Bateman really is: regardless of whether he murders various people and admits it, nobody actually cares as they're all so obsessed.