Beware learned helplessness. This is not an insoluble problem.
It has to be possible to get trafficking victims to not cooperate in their own enslavement. Which is what this is  

 - involuntary labor with the proceeds stolen. Slavery.  -

it is very difficult to effectively police a crime that goes unreported, but that is not inherent in this problem itself - unlike the drug trade where everyone involved are sort of acting on their own volition, trafficking has unambiguous victims - people who have all the incentives in the world to see the police nail the criminals,  who know who the criminals are, and where to find them. So there has to a way to make enforcement work.

I mean, taking it to the limit and making the penalty for pimping public execution, confiscation of all property and the distribution of it to your victims would work, no?