Ratzel: Under international treaty, there are (from what I understand) exactly two countries legally authorized to produce opium for medicinal use - Turkey and India, IIRC.

Those countries fairly strictly control the planting and cultivation of poppy, and are required to track it every step of the way.

I don't recall the financials, but I don't think Afghanistan would be very likely to have the sort of governmental infrastructure, or border control, required to be placed inside that system. (Simply authorizing production is a bad idea - illicit diversion is already a problem.)