[BroJoeK]

WarIsHelAintItYall: "Direct purchase of cotton by the 'factors' enabled the Southern growers to quickly turn a profit instead of waiting months for the cotton to be sold, and the money to return to them.
But this benefit also cut their profits."

In support of your argument, I'll reference possibly the best source.
However, it appears to me they and you exaggerate the importance of Northern shipping to Southern cotton exports.

Other facts should also be considered:

1. In politics for over 70 years, from 1788 until the election of 1860, Southerners dominated the Democrat party (and its predecessors)and Democrats dominated in Washington DC, nearly 90% of the time.
   So nothing happened -- zero, zip, nada happened -- which Southern Democrats strongly opposed, certainly including tariffs and US navigation laws.

2. That's why no US laws -- zero, zip, nada laws -- ever prevented Southerners from building, operating and profiting by their own shipping.

3. Many Southerners did build, operate and profit from their own ships, especially in ports like New Orleans and Baltimore.

4. During the 1850s nearly half of Southern cotton exported from New Orleans directly to international customers -- data from this source is key to my argument.
   It says: of New Orleans total exports only 15% went to Northern US customers.
   So there's no reason to suppose that Southern ships did not transport a very large portion of New Orleans exports.

5. Which ports did the other half of Southern cotton ship from?
   Well, as this map clearly suggests, mostly from other Gulf Coast ports in Texas or Alabama, and some cotton traveled by railroad to Northern cities like Philadelphia.
   So smaller South-eastern ports like Charleston & Savanah could not have shipped more than 20% of all US cotton.
   They were simply not that significant in the bigger picture:

   

6. Compare the map of cotton to one of 1860 Southern railroads:

   

7. Finally, notice the regions and products for other Southern exports:

   

WarIsHelAintItYall: "Business was business and our men in Washington ensured that we would have most of it."

Except they couldn't and they didn't.
By 1860, 80% of Southern cotton exported from Gulf Coast ports in ships which could as easily have been Southern owned as Northern.
So South-East cotton picked up by Northern packets for transshipment in New York or Philadelphia was just a small portion of the total.

SS Planter, built in Charleston, SC, 1860, loaded with 1,000 bales of cotton:

[DiogenesLamp]

The trouble with you is that when someone asks you for the time, you explain how to build a clock.

:)