Here's a quick guide to dealing Narcotics...
They're produced by Agricultural and High-Tech systems. If you can find one controlled by Archon Delaine, the output is given a little boost, meaning more quantity available at a cheaper price. Around 8.3k per unit is a good price to buy from.
They're consumed by the workers of Extraction and Refinery systems, seeking to alleviate the drudgery of their day-to-day lives. Also popular with the hedonistic youth of Tourist systems. Find one of these system with a black-market (a stupidly easy doddle, given that they're all revealed on the System Map

). If you can find one in system exploited by Delaine or Antal, even better - you'll get a 10% bonus on the black market.
Around 10.7k - 11.1k is a good selling price.
My current run nets me 2.8k per unit, over a single jump