http://en.wikipedia.org/wiki/Drug_Enforcement_Administration#Impact_on_the_drug_trade
"In 2005, the DEA seized a reported $1.4 billion in drug trade related assets and $477 million worth of drugs.[18] However, according to the White House's Office of Drug Control Policy, the total value of all of the drugs sold in the U.S. is as much as $64 billion a year,[19] making the DEA's efforts to intercept the flow of drugs into and within the U.S. less than 1% effective. Defenders of the agency's performance record argue that the DEA has had a positive effect beyond their relatively small annual seizures by placing pressure on traffickers, raising prices for consumers which may reduce the affordability of drugs [citation needed].
Critics of this theory (including the Nobel Prize winning economist Milton Friedman, prior to his death a member of Law Enforcement Against Prohibition) point out that demand for illegal drugs is inelastic; the people who are buying drugs will continue to buy them with little regard to price, often turning to crime to support expensive drug habits when the drug prices rise. One recent study showed that the price of cocaine and methamphetamine is the highest it has ever been while the quality of both is at its lowest point ever.[20] This is contrary to a collection of data done by the Office of National Drug Control Policy, which states that purity of street drugs has increased, while price has decreased.[21][22][23] In sharp contrast to the statistics presented by the DEA, the United States Department of Justice released data in 2003 showing that purity of methamphetamine was on the rise.[24] Ironically, this information was provided to the USDOJ by the DEA."