The value which an actor surrenders for another value can never be greater, for the subject himself under the actual circumstances of the moment, than that for which it is given. All contrary appearances rest on the confusion of the value actually estimated by the actor with the value which the object of exchange in question usually has or has by virtue of some apparently objective assessment. Thus if someone at the point of death from hunger gives away a jewel for a piece of bread, he does so because the latter is worth more to him under the circumstances than the former.

Georg Simmel, on individuality and social…, loc. 240