But no man wishes to buy a thing for more than its worth. Therefore no man should sell a thing to another man for more than its worth.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic worth wish
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/18755/pg18755-images.html

Context

“Therefore, in contracts of buying and selling, it is lawful to give a thing in return for more than its worth. On the contrary, It is written (Matt. 7:12) : "All things . . . whatsoever you would that men should do to you, do you also to them." But no man wishes to buy a thing for more than its worth. Therefore no man should sell a thing to another man for more than its worth. I answer that, It is altogether sinful to have recourse to deceit in order to sell a thing for more than its just price, because this is to deceive one's neighbor so as to injure him. Hence Tully says” source