They paid 72% of the taxes. That's why the nation wanted to keep them.
If you think it was because of slavery, you are naive. They wanted those states to remain in the Union so they could keep getting that money. It's simple human greed. Nothing moral about it.
Again, you are nuts. There was no tax on exports. The planters were not paid in British pounds. They were paid in dollars by the Cotton Factors who actually sold the crop. Those Factors moslty represented Northern banks. Your beloved slave driving planters paid little or no tax, and again I say without a doubt, you are nuts!