Do quality leeches worth something? Anyone with an established character can grow them, but it takes time, lot of time.
Leeches damage grows linearly, making them capable of dealing 90 total damage at q100, thus a plenty of leeches can kill most players without murder. And I find them easier to heal myself than with bandages.
I'd gladly sell some of my bloodsucking assassins and healers if there were any people that would buy them for a reasonable price.