On any type of complex work, it takes more effort to tell the difference between passive resistance to enslavement and limited skill or ordinary mistakes that the brutal style of slavery practiced in the slavery era US southeast is impractical. It's simply easier for a slave overseer to do the job himself than to watch a technical slave do the job closely enough to see that it's done right.
Instead, something more like a benevolent Roman slaveholder would be necessary. Imagine a Roman trader with a Greek translator handling his business correspondence with Greek associates. The Greek could easily include a note to offer a huge kickback to the correspondent to buy his freedom and bring him back to Greece. To keep the Greek from cheating him, the Roman owner had to gain his loyalty. That would include lots of priveleges (good food, slave women, etc.), the right to accumulate his own money and eventually buy his own freedom, legal rights not to be punished too brutally (by Roman standards), and other things that are not at all like a US field slave's conditions.
(It wasn't like that for all, or even most, Roman slaves. A mining slave, for example, might have the legal right to keep his own money and buy his freedom too, but the work was so exhausting and dangerous that practically all of them would be dead from overwork or injury in less than a year, long before they could buy their own freedom.)
So, if you want to allow slavery for complex jobs, think about that hypothetical Greek translator, not a US field slave. And in terms of the market price for a slave, it should be only moderately less expensive than the amortized cost of paying a free employee -- maybe five years of salary.