It would therefore seem that their tolerance had been reduced since the first shot. Someone conjectured that tolerance was partially a matter of place-conditioning and that addicts who shoot in a particular gallery get conditioned so that their body begins to gear up for a shot when they go their and that therefore they have higher tolerance there. This model works pretty well for cigarette companies. However, it is totally off the mark with respect to H sellers. To begin with, as Big Bill Burroughs has documented, the model is empirically wrong since there is no clear distinction between users and sellers.
Most users sell to their friends, making a little profit.
In the social network of users, some will sell on a large scale, but typically not for a long period of time, as it is a hassle. The only real organization in drug dealing is at the higher levels where the drugs are purified, smuggled, and cut. Furthermore, ignoring empirical facts, the image of the pusher is pretty unsound. It only makes sense to spend time hooking people if you plan on selling to them for a long time and they will not be able to go elsewhere. Neither condition tends to be true.