You ignore my point that the blockade boosted the world wide competition to a level it would not have achieved without the blockade.
Foreign cotton farms could not match the production advantage of slave plantations unless they too were slave plantations.
The Slave plantations would have always been able to sell cheaper product, and so they could always undercut any foreign competition so long as they wished to do so.
Sure, eventually foreign cotton producers could get market share, but it would have been a long hard slough without the blockade giving them an instant market.
This seems like simple economics to me. Why can you seemingly not see it?
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.