Over the course of an average 79-year lifespan, a white individual contributes a net $220,805 to the system, whereas over the course of an average 75-year lifespan, a black individual receives a net $751,200.Calculate the NPV of a lifetime of resource consumption. Add in the fertility rate over 40 years. Deporting one female on welfare to Africa would be the equivalent of removing roughly 5 tax eaters.
Paying the straight NPV as a lump sum cash settlement leaves you with a net financial benefit of zero. This doesn't consider secondary effects such as falling crime rates and falling property values (prices would rise in heavily black areas, but the net effect of reducing population lowers total housing demand and opens up more areas for white settlement).
These calculations also do not consider government employment. If government jobs are a form of subsidy, the cost of keeping blacks in America is much higher than estimated.
Flip it around. Assume the government obtains a piece of empty land in Africa to resettle current citizens. Natives are resettled, this land will only be home to former U.S. citizens. Assume the government is paying a large lump sum, plus free housing and developed infrastructure, in return for giving up citizenship and having your own independent nation. Would you take the deal?
There's no need to repeat the mistakes of the Civil War. Buying peace is far cheaper than it appears. The deportation part will be met with resistance, but bigger numbers in the lump sum payment will overcome a lot of it.