Well occasionally there are NBA players who put up a ton of points. Iverson is the type of guy who takes 25-30 shots a game, and if he can hit 40% of then he normally ends up with around 30 points. So he just hit a higher percentage of them. He also made a ton of free throws too... was it 24 out of 27?

But yeah, at least once a year there is a performance where someguy gets more than 50 points. It's nothing too uncommon.