The fallacy is in equating criminal activity with stupidity. This fallacy might stem from assuming that the risk was immeasurable and the profit therefore potentially negligible (bayesian inference).

Arithmetically inclined individuals being advantaged as sellers leads to survivorship bias. It's not actually surprising that a salesman can do that. It's surprising that drug sales can score huge gains and that some people see hardly any alternative to make a living even if small time dealers hardly make a profit because of oversupply in competition, much less if they are addicted.