Adult human semen, when donated to a sperm bank or fertility clinic in exchange for money... usually around $50 a donation. Often a source of quick easy funds for college males.
Frat boy 1: "Can you go in with us for a keg this weekend?"
Frat Boy 2: "I'm broke now, but I'll have 60 bucks to chip in after I drop off some white gold."
Frat Boy 1: "So you've managed to turn your hobby into a business, I see..?"