Imagine a world where it has been discovered that male precum contains certain compounds that can be processed to produce highly addictive, mind-altering drugs. These drugs have incredible medicinal potential, but are also dangerous, and so are tightly controlled by governments.

Comparatively large amounts of precum are required to make the drugs, so methods of artificial synthesis are preferred. But the secrets of these methods are tightly guarded and prohibitively expensive, so naturally a precum black market develops.

Kidnapping and enslavement turns out to be a turn-off for most men, so the black market comes (hehe) to rely heavily on men who are paid to be edged and denied. In short, to produce as much precum as they can.

A market also develops, then, for people who can maximize the precum that can be extracted from these men. This is of course achieved with much teasing, edging, and denial, but also balanced with occasional release and downtime. Every man is different, so this skillset is very much an artform. A man can act as a free agent if he wants, but by employing a good "milker," he usually stands to earn a great deal more money. And have a lot more fun while he's at it...