The US War on Drugs is ridiculously harmful and shortsighted, absolutely. But the sentencing is consistent with US policy, however wrong it is. People are getting two-figure sentences for carrying small amounts of drugs themselves. Someone who facilitates the selling of an illegal product on a much wider scale should not get a lighter sentence.
The whole concept behind the War on Drugs sucks, but this sentence is consistent. If it were a shorter sentence, then it'd be similar to the legal inconsistency around cocaine: the form wealthy white people tend to use (powder cocaine) is much less penalised than the form poor and minority people tend to use (crack cocaine), because...?