As an example of rational behavior, drug dealers approach their profession in a(n) fashion

As an example of rational behavior, drug dealers approach their profession in a businesslike fashion.
For drug dealers, their job is the same as any other job - and they want to be professional about providing their customers with the product they want and need. They also want to be respected, as well as paid properly for what they are offering, regardless of whether the goods are legal or illegal - it's business.