The price the farmers get is a lot less than the jack-up by the middlemen. The total "farm gate" price of opium in 2005, if I'm interpreting the term right, was about $600 million. This is not chump change, but not beyond reason, either.

You are right that market forces would increase the problem in the long run, unless somebody can find something more lucrative that can generate that kind of cash. Nothing comes to mind.

However, the middlemen, which often consist of criminals, and people funding terrorism, racked up about $2.2 billion in profits on that $600 million in farm product. Buying direct from the farmers would take an awful lot of cash out of the hands of those middlemen.

U.N. Report