The punk style originated as an imitation of post-apocalyptic existence. You can see this in the tattered clothing of punk rockers, and also the skeletons, skulls, and atomic bombs you see exploding on punk rock merchandise and album covers. There is a lot that is "fiendish" about punk rock.
In the post-apocalypse, how much money you have would not really matter much, and you would have to fight for your life like an animal. This idea is reflected in the lyrics of many punk songs, a clear example being Anarchy in the UK, by the Sex Pistols. "I am the anti-christ, I am an anarchist, don't know what I want but I know how to get it." The ideas expressed in this sentence reflect many people's ideas about the apocalypse (anti-christ, anarchist).
Punk came about as a reflex to the "push-button" culture that originated in the 1950s, a culture that sprung up with much help from the United States' emerging "Super-power" status, which was, in turn, helped by the fact that the U.S. possessed, and had already USED, the destructive power of Atomic Bombs. People used vacuum cleaners, washing machines, televisions, many household objects were operated at the push of a simple button; and the belief that the world could be destroyed in a nuclear inferno at the push of a button was a huge catalyst in the development of the punk attitude, and the "I dont give a shit about anything" lifestyle.
Punks are notorious for hating people who have their heads up their asses, people who blindly invest their souls into capitalism, and their have been millions of these people for punks to hate since World War 2.
Punks dressed like they did because punks felt that punks were the only people with whom eachother could sympathize about the wrongness of the main-stream. With the way punks dressed, a punk could automatically tell if somebody hated the same things as he/she did.