With the demand for lean today and the high prices that it could fetch, I'm surprised that no one has ordered large quantities of codeine and promethazine tablets from India and tried to create their own syrup. I know that people say the taste of lean is better than the effects, and a homemade blend would probably taste like shit, but still I would think there is a market out there.
While there is a bit of minute demand, most people here are looking for something... better. Lean is expensive and weak, and more of a status quo drug than an actual, enjoyable experience.
I can see making some sales but the market for lean is typically not the same market as the darknets.