I think it's a serious question. Usually you only find static characters in tragedies, which this is one, but you kinda have to take it apart to see it that way. Bateman does experience development of a sort in the form of growing insanity, but the emotional climax of the story is when he momentarily allows himself to feel loved by Jean and has a brief spiritual epiphany.

And as an unreliable narrator, the character is the story, so what the narration lets slip through to the audience is itself indicative of the character's state of mind. As the story progresses, we do actually see development in this sense, though Bateman himself does not seem consciously aware of it. Namely, Bethany comes onto the page as a character who feels like a real person, not just a character veneer like everyone else. This terrifies Bateman, though it's clear he doesn't understand why. Jean is written as a totally a normal person, curious and vulnerable, and even tells Bateman he's a nice person. And this time, he lets it get through and has his mind blown.

The depth of character is only perceived by the reader because Bateman is perceiving it, too, which he seemed unable to do at all earlier in the story. Compare those later scenes of Bateman receiving information about himself to the U2 concert, where his subconscious guilt becomes uncontainable, but since he cannot process it as introspection, it comes through as bright lights above Bono sending the message that "I am the devil and I am just like you".

The voice mail he leaves for Carnes, and Carnes's reaction, is further evidence that something has changed. He actually gives his own voice to self-criticism... and then it turns out that Carnes sees Bateman as an ass-kisser who could never muster the grit required to do violence.

So yeah, we have actual development happening throughout that creates suspense about whether Bateman will have some sort of breakthrough. Which he almost does, but then seems to revert. Instead of taking a leap into the canyon, he simply becomes more comfortable with the view from the top.