That's stupid dude and a empty argument (save stopping organized crime which in the case of drugs will just allow them to convert to legit operations). Legalized drugs is working fine in Amsterdam and is affordable. Same goes for prostitution in Amsterdam and Nevada. It's expensive now, and people have the ability to by it as easy as making a trip to the market.
What would be good is the government would be able to tax it. What makes it expensive now is trouble it takes to get illegal substances into the black market place.
Doesn't seem to be "working fine" according to this article (about a year old):
Amsterdam draws curtain on sex industry as red light windows closeLast updated at 13:38 21 September 2007
Shut up shop: A third of prostitute windows set to close
Amsterdam is set to lose a large chunk of its red light district, after the forced sale of a third of the buildings currently used for prostitution.
With its scantily-clad prostitutes posing in brothel windows and coffee shops oozing the pungent aroma of cannabis smoke, the red light district's seediness has always been part of its attraction.
But the district is a magnet for petty criminals and, authorities believe, human traffickers, drug lords and mobsters - who take advantage of the situation to launder money. Amsterdam: the red light district's seediness has always been part of its attraction
Cracking down on prostitutes: Amsterdam Mayor Job Cohen
The move is part of Mayor Job Cohen's efforts to counter that crime.
"What we do want is to get rid of the underlying criminality," said Cohen.
He insisted however that he didn't want to get rid of prostitution entirely, since it is part of the area's history and a major tourist draw for the city.
It is understood that the buildings could be turned into luxury apartments and tasteful shopping malls.
The NV Stadsgoed housing corporation has purchased 18 buildings with 51 windows, that have traditionally house window prostitutes in Amsterdam's famed red light district, for 25 million Euros.
That is around a third of the windows in the red light district, though there are other prostitution zones in the city.
NV Stadsgoed will redevelop some or all of the buildings, and because they are not likely to be worth as much as housing or regular commercial real estate, the city has agreed to reimburse the corporation by up to 15 million Euros.
Amsterdam has been conducting a crackdown on crime in the city centre for nearly five years, using a 2002 law that forces business operators to disclose detailed accounting in order to have their licenses renewed.
The seller in deal, "Fat" Charlie Geerts, was ordered by the city last year to close the windows because the city said he failed to meet standards.
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Shut up shop: A third of all the prostitute windows are set to close
But he filed a legal protest and Amsterdam's District Court granted an injunction against closures while he fought the decision.
Prostitution is legal in the Netherlands, and coffee shops are licensed to sell small amounts of marijuana.
Prostitutes' rights organizations have generally been indifferent to the crackdown, arguing that pimps are the main source of problems, not landlords.
http://www.dailymail.co.uk/news/article-483075/Amsterdam-draws-curtain-sex-industry-red-light-windows-close.html