This is side-note on a remark in Nikolai's note.
I wanted to bring to general attention that while the movement against
slavery in the 19th Century was spearheaded by opponents impassioned by
humanitarian concerns, its ultimate elimination was not without economic
benefits for the owners.
While slavery was more coercive and appeared cheaper (which was why it
was the most favored form of labor control initially used by the cutting edge
of capitalism during its initial expansion), over the long run it was more
expensive than wage labor. It compelled the owner to eventually assume the
costs of reproduction, and it imposed a low ceiling on productivity. The wage
relation solved both of these problems at once. By shifting the reproduction
cost to the laborers, it provided them an incentive to work harder while at
the same time liberating the owner from the necessity of paying a "living"
wage.
--Peter Grimes