They were self sufficient as far as that went, but cutting 200 million out of your economy in 1861 would have caused a financial panic. It would have slowed down growth and probably caused a big upspike in unemployment.
My point is, the financially powerful people of New England did not want the South to secede because it would crush much of their finances, and their former customers would become competitors.
No, Southern secession was a dire financial threat to the New England economy.
Before he took office, New York was making plans to secede. When the Confederacy announced its much lower tariff rates, governors and businessmen clamored for war.
Lincoln accommodated them by invading Charleston and Pensacola.
No, Southern secession was a dire financial threat to the New England economy.
Now you are just being silly. Big cotton men in New England wanted the supply of cotton from the South to keep coming. It wouldn't have been affected by the tariffs and if the Southern tariffs were as low as you say, New England mills could have sold their products in the South just as they did before disunion. Textiles were the driving engine of the New England economy and textiles relied on the North-South trade of raw cotton and finished fabrics.
What else were New Englanders making? Pots and pans, I guess, that they could sell South and West as well, but the idea that secession meant a "dire financial threat to the New England economy" is nonsense. If Southerners really were going to start their own cotton mills it might have been different, but the rebels weren't about to do anything like that at the time. The whole point of low Confederate tariffs was that they didn't want to develop manufacturing.
The Northern response really was about non-material factors.