And so the reason.
One of the Twelve Possessed would fetch the same price as a country – if they were able to obtain all twelve, they stood to win themselves an astronomical sum of money. Equivalent to obtaining access to a mountain rife with gold.
That would be enough – although practically speaking, even three or four of the Twelve Possessed was plenty – enough to save Maniwa Village.

Katanagatari Omnibus 2, Page 22