First off, that's not a quote of Dilorenzo. It's from a college level economics textbook. Second, it does not say that exporters are the only ones that swallow the costs of a tariff - it says that they are the ones who are hurt the most because they, more than anyone else, cannot do a thing about it to pass on the costs. Third, the reason this is so has to do with the fact that exporters are ultimately unable to avoid the economic costs of a tariff, which is in the destruction of trade.
The Northern wheat farmer is no more able to add to his price to cover his additional cost for imported goods than is the southern cotton exporter.
You are missing the issue entirely, non-seq. The northern wheat farmer may indeed have to pay higher prices because of the tariff, but that is not where the worst cost of it occurs. Tariffs hurt exporters the most because they kill off trade. If trade does not happen, exporters do not make money. The south made 75% of the nation's exports and had an economy that made its money almost entirely off of them. If you kill off trade, the region that gets hurt the most becomes a simple matter of mathematics. Which do you think it will be? The region that provides 25% of the nation's exports or the region that provides 75%?
And why are they, more than anyone else, unable to pass on their costs? That's the question I keep asking without getting an answer? The cotton farmer was at the mercy of market prices and so what the wheat farmer and the factory laborer. None of them could arbitrarily raise their prices to make up for a hike in tariff. All were equally hit.
Tariffs hurt exporters the most because they kill off trade.
How did a hike in iron tariffs kill of cotton exports? Did the textile manufacturers suddenly stop making cloth and switch to iron? Did the tariff on iron cause a glut of cotton on the market and ruin the price? Where is the connection? Did the high tariff's of the 1840's cause cotton exports to drop?