Its obviously not a black/white situation. However, the single act of making the drugs illegal, not only sucks away our own government's money via the war on drugs, but also the simple risk/reward rule comes into play here. The fact that the drugs are harder to obtain, makes them more valuable when they do get here, and if there is money involved, there will be no shortage of dip-shits trying to bring/produce the drugs here in the US. So the illegality of all these drugs makes it much more profitable to move/produce them. Our intent is to fight the war on drugs, but really we are just giving the criminals/drug cartels massive funding, because the illegality of it, is what makes drug dealing/smuggling so profitable. We are funding these whack-job criminals and drug lords, by making it harder to obtain the drugs here in our own soil.
It also makes people more likely to do other illegal activities, to obtain the money to spend on the drugs. IE: breaking into your house to steal your tv, mugging you, robbing an old man of his heart pills to sell for other drugs, rob banks, etc etc.
I think the focus should be on as unholy said, education and treatment over punishment/enforcement. Granted many a job would be lost if we just ended the war on drugs altogether, but new jobs would spawn from the other approach. You obviously wouldn't want to dispose of the DEA and other agencies right away, but instead swing their focus to drug issues that spawn here within our home borders (IE: meth, bath salts, regulating pharmaceuticals - this one is huge, and regulating the new medical marijuana craze - some states have legalized marijuana, and it is much easier to smuggle anything from state to state, vs going through customs or trying to avoid them).