I dunno enough about 80s fashion to pick up on it myself but apparently if you do, it becomes increasingly noticeable that the outfits Bateman's describing are completely bizarre and nobody would ever have worn them.
Hmm, I hadn't noticed that about the fashion either but it's certainly the case with the food, which often sounds both opulent and horrible - pan-blackened king prawns in a bitter chocolate sauce, etc. etc.
If this gets progressively more pronounced as the book goes on then I suppose it's a warning about his increasing unreliability as a narrator? It's a neat idea. Actually it's a good example of a book that's very cleverly written without ever beating you over the head about how clever it is.