Setting up a lab capable of producing fentanyl has significant up-front costs associated with it. Running the lab and keeping it stocked with precursors is an ongoing risk. For better or worse, the golden age of american clandestine laboratories is probably past: it is far easier to import an uncontrolled, custom-synthesized fentanyl analog, although I would not recommend getting into this business.

Fentanyl isn't popular _at all_ among opioid addicts. The duration of effect is short relative to morphine-like molecules and it absolutely wrecks one's opioid tolerance. Fentanyl is popular among unscrupulous heroin dealers that try to pass off a cheap synthetic opioid as $200/gram diacetylmorphine.