Here are some stats on recent seizures of illegal drugs. Too many are accidental seizures of drugs in stops unrelated to the actual movement of drugs as a result of infractions that lead to the discovery of drugs.
GPD seizes $290K worth of Marijuana (Sept 17, 2011)
CBP seizes over 11,000 pounds of pot at Nogales port
Mohawk carries 37 bales of cocaine weighing over 2,600 pounds (with an import value of $83 million)
No matter how you cut it, this is big business at all levels of law enforcement and it is big business because a lot of people have the disposable income available to buy it.
It would be an interesting experiment to see just how much the repression/recession has impacted on the drug trade.