Besides the quality of the drugs a vendor sells what differentiates a good vendor from the bad? And a professional from an amateur? I am certainly not trying to become "the best vendor" but what I want to become is the best vendor by my own capabilities and set some sort of high standard which will make customers come back.
Amateur vendors want to be Walter White presiding over a Darknet Empire.
Professional vendors want to be eBay sellers with drugs and bitcoins.