Basically a running theme of the book that's not really conveyed well is that everyone in Patrick Bateman's world is a bunch of narcissistic borderline psychos, so they frequently mistake each other for other people and don't give a shit about anything except the outward appearance of being normal and super successful. So at the end, Bateman's just talking about how empty and meaningless the story/his introspection is, because he's trapped in his routines and/or possible mental illness and can't escape (there's even a "No Exit" sign behind where he sits).
Yo.
Yo I like that.
But thats The Shining levels of not conveying certain themes very well. It's okay tho.