Very good questions. This reminds me of the central question in "Zen and the Art of Motorcycle Maintenance" by Robert Pirsig. This timeless classic has the protagonist touring the country (the U.S.) by motorcycle as he pontificates on the nature of Reason. What is it? What value does it hold for the human race? How does one achieve it? Etc.

The principle quality of value is subjectivity. What is valued by one person is not valued by another. Again, what one values at one time may not be as valued at another given time. Water to a man on the verge of dying of thirst, for instance, will be highly valuable, but to a man who just had a drink in the comfort of his own home and in no danger at all will have less value.

Good question, though. Keep asking it. We might arrive at the answer some day.