I live in a country where prostitution is legal (Germany) and have had sex with prostitutes before and plan to do it again in the future. ( maybe even this week. Haven't had it in a while

)
The following is based on my own experience and on reading a message board about prostitution in my city (The board is run by customers for customers, but a few working girls and brothel operators are registered, too)
Prostitution will always be there, no matter what the law says. Even in very repressive muslim countries it's easy to find prostitutes if you know where to look.
It's like alcohol or other drugs. Prohibition doesn't make the good in question disappear from the market. It only turns the people involved into criminals and grants criminal organization a virtual monopoly.
There is nothing wrong with the exchange of money for sexual services. What's wrong is the involvement of organized crime and pimps.
If you want to protect women from exploitation, then you have to fight organized crime, not prostitution itself.
Organized crime is rampant in all industrialized countries and yet it's rarely spoken about. THAT is the issue.