How much east African heritage do African Americans have, or are they exclusively of west African and European descent?
Yes, their position in autosomal PCA charts is unique because of their admixture, thats why they are pulled in the East African and direction from west African.
A good quality unskilled slave would be around 34,000USD. A skilled slave might be double that. Of course, that's just taking the slave costs in the 1800's and doing inflation adjustment. Since market demand now would be lower (due to the fact that most people find slavery abhorrent), the price would be lower as well.
The fixed costs for keeping a slave would probably be around 50-100USD a day, based on how much it takes to keep inmates in a prison.
I think those numbers are going to be artificially low, since most of it is people going around to starving families and saying "I'll buy your daughter and pay for a month of food."
I think you'd want to look at how much pimps pay to trade high-end call girls (or however that industry works), but I'm really not savvy enough to go out and talk to a pimp.
South Carolina, 1800-09 prices $381 ( http://cliometrics.org/conferences/ASSA/Jan_00/rosenbloom.shtml )
Using Measuring worth treating a slave as a capital good (nominal GDP/capita):