In a previous post, Zippy comments:
I would suggest (without pretending to approach an exhaustive account) another factor: contextual. Generators really are more valuable during a widespread power outage, etc — not because of convention and not because of the generator’s intrinsic powers, but because of the external objective situation.
Let us consider this contextual value.
It seems correct to say that in the context of a blackout generators are more valuable. However, why are they more valuable. We wish to know in what respect the context relates to the value of the generators.
The reason the generators are more valuable is because the blackout causes a greater need for them. This need is wrapped up in the further context of the environment and the expectations of the people suffering the blackout. However, it is the need as such which is the cause of the greater value. We see this in that in the context of a blackout, people on the street do not find the generators more valuable for themselves.
Context is then accidentally related to value and may be the cause of the need, but it is the need as such which is the foundation of value. Indeed, value consists in the coordination of the finality of the person in the object of desire and the finality of the thing to produce that object. Every desire takes place within a context, but it is not the context as such which is the cause of the value.