Turns out this is has been question for a long time.
The question of the ‘just price’ is as old as Western civilization and of continuing relevance and concern to it.
In ancient Greece, Aristotle considered it;
in medieval Europe, St. Thomas Aquinas and his fellow Scholastics pondered its mysteries;
in the age of conquest, Mercantilist economists re-considered it as New World gold and plunder poured into the coffers of European kings and queens;
at the dawn of the Industrial Revolution, Classical economists from Adam Smith to John Stuart Mill struggled to answer it;
Karl Marx re-established its moral imperative in the exploitation of labour;
at the height of the Industrial Revolution (about 1900), Alfred Marshall and the Neo-Classical School seemingly resolved it through interaction of supply and demand in a perfectly competitive marketplace;
in the pre-dawn of the Atomic Age, Keynes shifted the question from individual markets to the economy as a whole; and,
today, in a post-modern ‘knowledge-based economy’ we continue to seek an answer
here, read the rest ....
Okay, never mind, maybe you don't want to read it, it's all economic mumbo-jumbo. Suffice it to say that the question of fair trade is one that some people have Deep Thoughts about.