Fair enough, IF:
First deduct the cost [in today's dollars] of: The U.S Navy's participation in anti-slave ship patrols before the Civil War, the cost of the Civil war after the effective date of the Emancipation Proclamation, the cost of Reconstruction, the costs of any welfare program that has overwhelmingly been used by Blacks, the costs of affirmative action in loss of opportunity for better qualified non-Blacks, the costs of lawsuits, etc.
Getting an accurate number [with proof] of the number of blacks ACTUALLY descended from slaves, giving a tax write off to every non-Black descended from immigrants who arrived after 1865, and any American resident from before that year who can prove their ancestors owned no slaves.
Oh yeah, and be sure to include in the payor class, Blacks, and Indians who owned slaves.
And, if after that, they owe us more than we owe them, figure out how the government goes about collecting...