A very pedestrian analysis. The north dominated in manufacturing at the time, the south had more agriculture because of the warmer climate.
The South did 500 million per year in trade with the North, and 200 million per year in trade with Europe.
The reason the South did so much trade with the North is because the laws had rigged everything to force the South to buy from the North.
They could have bought much better industrial products from Europe at cheaper prices than they had been paying, but because the laws forced them to pay higher prices for European goods, they were forced instead to purchase Northern goods and services.
The North was getting about 60% of all the money the South produced in it's trade with Europe. Most of it going to DC. I believe they were paying 65 million in taxes per year.
All of this in an approximately 4 billion GDP economy.
The South's 700 million in trade was a significant part of that economy.