The Trip From The The Tibetan Plateau,

to the shops,

 makes these the most expensive parasite in the world, Yartsa Gunbu, (Ophiocordyceps sinensis), it is a fungus that infects ghost moth caterpillars on the Tibetan Plateau, fetching up to $50,000 a pound, photograph Deepak Raj Bhatt/Wikimedia Commons, it has a convoluted lifestyle, have a look here for the full story,

Yartsa Gunbu shop, Tibet, photograph Erik Torner/Flickr, from humble beginnings, Yartsa Gunbu is a good way for local communities to supplement their yearly earnings, in Bhutan, for example, the fungus trade makes up a considerable part of the gross domestic products, and in many Tibetan villages, harvesting the fungus is one of the few ways for families to sustain themselves, usually selling Yartsa Gunbu for only a few hundred dollars per pound, 

 but, passing through chains of middlemen, the Yartsa Gunbu parasites reach Hong Kong and bustling metropolises in mainland China, where they sell for ludicrous amounts of money, according to The Atlantic, the global market for Yartsa Gunbu was worth between $5 and $11 billion, with the finest specimens of the parasite selling for up to $140,000 per kilogram. But even cheaper specimens are highly coveted in China, where even members of the middle-class have started spending small fortunes on it, taking it as a prophylactic against all sorts of conditions, when ever I read of this sort of thing, I always wonder, how did someone find out about this?