In Huston's book, "Calculating the Value of the Union", his table 2.3 (page 28) lists 1860 census results for values of various categories of property, and "property", ahem.
These numbers are for the entire Union:
Sherman Logan: "the $500 average price of a slave in 1850 equates to somewhere between $11,000 and $162,000 today."
In overall economic terms, it's more than that.
For real apples-to-apples comparisons, I think you need to look at their "relative share of GDP" number, which corresponds to "how much national effort went into this project", and that number would today be $1,740,000.
So four million slaves then, at $500 per slave, corresponds to about $7 trillion dollars today -- a pretty hefty sum.
But the census total of $3 billion suggests an average cost of $750 and equates to more than $10 trillion today.
Finally, we should note again that $3 billion in slaves was more than the value of all Southern lands themselves, and more than the total Northern investment in railroads and manufacturing.
So the potential loss of such value through some actions in Washington DC, was certainly a matter of utmost concern, not just to large slave holders themselves (relatively few), but to every Southerner whose prosperity depended on their "peculiar institution".
Interesting.
Assuming the numbers are more or less accurate, the value of the slaves alone (not counting the value of their production) was 3x the capital invested in the overpoweringly dominant industrial sector located largely in the North.
/s
The South was indeed oppressed and exploited after the War, and I believe people tend to move this oppression back in time and assume it was the same before the War.
But the truth is, as has been pointed out on this thread several times, that the South was actually dominant and rebelled because of seeing the writing on the wall that this dominance was ending, not because of intolerable oppression.
I am always amused by those who repeat the canard that the South seceded to resist expansion of federal power, when the actual issue that broke apart the Democratic Party, the last institution joining the sections, was a demand for expansion of federal power.
The southern delegates demanded that the Party add to its platform planks insisting that northern state laws giving fugitive slaves something resembling due process be repealed, and that a federal slave code impose slavery throughout the territories, using federal troops to protect the institution against the wishes of the inhabitants if necessary.