Slavery was producing 72% of the total revenue for the Federal government in 1860. It had been producing the bulk of the tax revenue since the 1820s. Pretty much everything connected to government during this era was paid for by the slaves.
When you look at the Capital accumulated in the South, most of it was in the form of slaves.
My recollection is that it was roughly equal to 4 billion dollars in capital investment that simply vanished with the Union invasion of the South.
Are you counting tariffs to be revenue produced by slaves?
Most of the federal revenue was from tariffs.
The federal government was very small at the time, a tiny percent of the gross national product.
Or so it was claimed by pro-Southerners at the time, based on the value of Southern exports in relation to Federal tariff revenues.
But a truer picture is much more complicated because, for starters, Southern exports were not 100% based solely on slavery.
Southern exports also depended on massive "imports" from the North of everything from capital (bank loans) to industrial products like railroad and telegraph equipment, to ships for freight, to farm tools, household goods, clothing and some food.
Because of this, foreign imports (and so Federal tariff revenues) did not flow into the South in proportion to their exports, but rather were sold everywhere in the US, depending on each region's relative incomes.
Wealthier cities imported more foreign goods, and so paid more of Federal tariffs, while poorer areas imported less.
Which brings us to the question of where, exactly, was the nation's wealth, per capita -- North, South, East or West?
The answer may surprise you, it did me.
As reported here, the average annual per capita income (APCI) in 1860 of various regions was:
We should also notice, the claim of "72% of Federal revenues" allegedly "paid for" by "Southern Products" can only be made by exaggerating Southern exports and minimizing exports from the North and West, especially by not counting California gold or Nevada silver as Northern exports.