I remember watching an episode of Tales From The darkside many many years ago where standard currency was non-existant and goods were purchased by exchanging your life force to another person.
I've been wanting to homebrew something like this, but I've never gotten the chance.
Original Formula:
Formula 2.0:Code:1 Copper = 3 Days
1 Silver = 1 Week
1 Gold = 1 Year
1 Platinum = 10 Years
Formula 3.0:Code:1 Copper = 1/7 Day
1 Silver = 1 Day
1 Gold = 1 Week
1 Platinum = 2 Months
Code:1 Copper = 1/14 Day
1 Silver = 1/7 Day
1 Gold = 1 Day
1 Platinum = 1 Week