Even air and water should be viewed as subjectively valuable, economically speaking, in my view.
In order for these to be valued, humans must first value the for their ability to sustain life. If someone doesn't value his/her life, (a tragedy) air and water no longer have value to this individual actor, really.
An extreme example, but good for the thought exercise.
Something that will soon be among the most dire of issues: air and water! Love the Zen reference too.
IMO, I don't think we need to go much further than perception. You either perceive a value or you don't. If there is no perception, there is nothing to talk about. A value is an abstraction that permeates a consciousness. It does not exist anywhere else.