I'm just going to leave my theory here since I don't want to comment on YouTube, but i want to share my thoughts and kiki asked for it. But this movie is about how, despite how seemingly powerful and narcisistic Bateman is, he is actually quite pathetic as a character.
He is seemly comfortable in his life but in reality he does everything in his power to keep his current lifestyle up, he has no hobbies besides those that aid him in maintaining his job and social and despite that he can't go up. He has reached the peak of what he can achieve, show by his constant inability to get into dorsia or having his greeting card be mediocre at best. In the end he is just another "cog in the machine".
He is definitely amoral, show by how he treats other who differ from him, but at the same time he is too sacred to do anything outright evil, seeing by how much he cares about how he is viewed (which is beautifully presented on the last dialogue he has with his lawyer, Bateman is too much of a coward to do anything like that) . So he is stuck where is, and it takes everything he can give to even keep his perceived social position. An example of this is how he pretends to be able to go to dorsia even tho he really can't, and how he ruins his chances with his secretary in order to continue to sell the fact he could go into dorsia if he wanted. That is right if you pay close attention he self sabotaged so that his inablity to get into dorsia wouldn't be noticed.
Confronted by the soul sucking reality of daily routine he fantasizes about killing people as a form of stress relive to the point where he starts to believe his own delusions. Even playing the the guilty part in front of the detective just because he needs it to feel alive, purposefully giving bad alibi even tho where he was could be confirmed by several people.
He then gets more and more lost in his increasingly fantastic delusions of killing people until he has a breakdown, going as far as calling his "lawyer" to confess his wrong doings. But at the end he is confronted with the reality that he actually did nothing of the things he dreamed of doing Paul house wasn't actually his house, the bodies where nowhere to be found Paul, actually went to London, the police where after him and there were not damaged in his own building. this puts him back into purgatory where there is no escape and he will sufferer forever thanks to his own mundanity. Which leads to the end dialogue, his confession meant nothing and there will be no release for him.
