You're halfway there with noticing everyone being so self absorbed to not notice the rich, hot guy throwing up red flags in front of them. People overlook a lot when you have money and looks. The second part is his affluency helping to erase everything. After he calls his lawyer, everything suddenly goes away. His lawyer, and likely his parents too, probably called in the cleaners to clear out Paul Allen's apartment, destroy all the evidence, and create alibi's like having lunch with Paul in London. The filthy rich can simply brush it all under the rug to protect their own.
If you liked this, you should watch "The Rules of Attraction". They are both books by the same author and "The Rules of Attraction" follows the dark and twisted love triangle between 3 affluent college students...one of which is Patrick Bateman's little brother Sean played by James Van Der Beek. He's quite the sociopath himself but not quite as psychotic as Patrick. Watch the Unrated version if possible. There are like 6 different edits for different countries because the original cut was deemed NC-17. The "Unrated" Blu Ray is the closest to that original cut.