In his January 1861 speech to the Georgia Secession Convention, Alexander Stephens said that 75% of the business done abroad, imports and exports, were done by Northerners. Government figures from the 1859-1860 period show that most import tariffs were paid in Northern ports by Northern consumers. In his speech Stephens also details how Southern postal deliveries were subsidized to the tune of over $6 million by the North. I think the claims that the South paid most of the taxes and received a disproportionately low amount of federal spending is just not supported by the facts.
I have never heard any mention of Southern post being subsidized by the North. Please provide a link. :-)