 Most contemporary scholars believe that sellers have wide, though not unlimited, discretion in how much they charge for goods and services. But there is an older tradition in business ethics, found in Aquinas and other medieval scholars, according to which there is one price that sellers should charge: the “just price”. There is debate about what exactly medieval scholars meant by “just price”. According to a historically common interpretation, the just price is determined by the seller’s cost of production, i.e., the price that compensates the seller for the value of her labor and expenses. More recent interpretations understand the medieval just price at something closer to the market price, which may be more or less than the cost of production (Koehn &amp; Wilbratte 2012).