Value is, always and everywhere, a subjective determination. Nothing has intrinsic value. A dollar, for example, only has value in that one can find someone else willing to trade for it. If no one is willing to trade for it, it is valueless.
An example of this occurs in Mass Effect 3. One of the side quests of the game involves Commander Shepard acquiring high end weapons for C-Sec (Citadel Security, the police force of the Citadel). C-Sec had originally contacted a black-market weapons dealer for the weapons. When negotiating payment, C-Sec offered Credits (the galactic currency) and the dealer refused. Commander Shepard is asked to work out a bargain. In conversations with the dealer, he says he’s refusing credits because, following the war with the Reapers, the credits will be useless. He is looking for something more physical.
Regardless of the right- or wrong- headedness of the dealer’s proposition, he did not value the galactic credits in the same way as Commander Shepard and C-Sec did. Although Shepard and C-Sec attached high value to the currency, the dealer did not. No trade would progress until the Commander was able to find something the dealer valued (in this case, artifacts).
Astute readers will notice a lot of overlap between this post and the preceding one. That is because this concept is built into trade, but it is such an important concept I thought it deserved its own post, especially as many laymen tend to think things have intrinsic value, especially commodities like gold, oil, etc. Things only have value insofar as they are useful.