The Deep South’s number one export, by far, maybe 10 to one, was cotton and South Carolina grew relatively little cotton.
So there’s no reason to think Charleston shipping was any more important than any other Southern port:
“Charleston was the leading city in the South from the colonial era to the Civil War. The city grew wealthy through the export of rice and, later, sea island cotton and it was the base for many wealthy merchants and landowners.”
http://www.oxfordbibliographies.com/view/document/obo-9780199730414/obo-9780199730414-0193.xml
1860 raw cotton exports totaled nearly $200 million of which at most 5% shipped from Charleston.
Rice exports totaled $2.5 million of which Charleston shipped maybe half.
Charleston was simply not a major player in the economic life of the South, regardless of what its promoters claimed.