Just Price
= The transaction value reached voluntarily by an informed buyer and an informed seller after a series of implicit or explicit offers and counteroffers, with neither under any compulsion to buy or sell. [1]
Description
From the Wikipedia:
"The just price is a theory of ethics in economics that attempts to set standards of fairness in transactions. With intellectual roots in ancient Greek philosophy, it was advanced by Thomas Aquinas based on an argument against usury, which in his time referred to the making of any rate of interest on loans. It gave rise to the contractual principle of laesio enormis."