You are ignoring the value of money and the living standards of various regions. Perhaps a poor peasant living in Turkey or China or India or Ethiopia or Brazil could grow cotton more cheaply than a slaveowner in Mississippi because of his low cost of living and low standard of living and the differences in the value of various currencies. But if you are still interested in this topic you can take it up with FLT-Bird.
Cheaper than a slave? A slave that could be forced to work all day long? It is my understanding that the slave plantations grew their own food, and so the monetary cost was effectively non existent.
I am having difficulty grasping how a group of poor peasants living in Turkey or China or India or Ethiopia or Brazil can produce a cheaper product than a slave plantation. (Weren't they using slaves in Brazil at this time?)
Other than shipping costs, I don't see a lot of variability, and that's *IF* shipping costs from Egypt were cheaper.