The culture of cocaine is deeply entrenched on Wall Street and some will pay more than its worth for the purest quality available. It’s a buyer’s market and dealers must compete to deliver first and close the sale, while keeping up with the changing Wall Street appetite. A new generation of brokers and traders are turning to a drug that keeps them performing at work. And police are coming down on a drug that they regard as Wall Street’s dirty little secret — which is quickly turning into an epidemic.