By 1860, cotton ruled the South, which annually exported two-thirds of the world supply of the "white gold." Cotton ruled the West and Midwest because each year these sections sold 30 million worth of food supplies to Southern cotton producers. Cotton ruled the Northeast because the domestic textile industry there produced $100 million worth of cloth each year. In addition, the North sold to the cotton-growing South more than $150 million worth of manufactured goods every year, and Northern ships transported cotton and cotton products worldwide.
So, if the price of Northern manufactured goods were increased by the Morrill tariff, the South would pay roughly 30 to 50 million dollars more for protected manufactured goods purchased from the North (assuming sales volume didn't go down because of increased cost and that all of the previous tariff went into the previous price of Northern manufactured goods). All this without an increase in the income the South was getting from cotton exports.
Northern people would pay more for their manufactured goods too, but that was money out of one Northern pocket and into the pocket of the Northern manufacturer. On balance, the North came out even, while the South paid.