I would say that there may be an economic standpoint to the differences in punishment for crack and cocaine... Still there are a couple of differences..
For one, 99% of the time, a gram sack of crack is gonna contain much more cocaine(around 30 %) than a gram of powder.. Also crack has been specifically manufactured in that form to provide a more powerful and efficient high than cocaine hydrochloride.. Not to mention, despite whatever rascism is involved, the cold hard facts show that there is more violent crimes and robberies surrounding crack as opposed to cocaine.. All these things combined, i would assume, would make crack legally more dangerous(i.e. more punishable) than powder..