Afghanistan Opium Survey- Executive Summary 2007
I'm a tad frustrated as I found the full report a couple of days ago and now can't. The UNODC link to the full report and other links take you here-the executive summary.
In any case, maqsad, total dollars captured by farmers, chemists, and traffickers approaches $2.8 bil. About $750 mil is held by farmers so the bulk would seem held by the traffickers and chemists, of which most probably lies in the hands of the traffickers.
My guess is that there's a very symbiotic relationship between the traffickers and the regional power-brokers/war-drug lords. Excluding farmers leaves about $2.0 bil (about 7% of the GDP, IIRC) concentrated near power-centers. Again, that's a lot of captal held within the country. Some sent overseas, no doubt. The rest-purchasing protection and grease for the economy on very favorable terms to the lender?