In recompense for 32 years of chattel slavery, any dollar amount would be a laughable pittance.
Of course, this doesn't take into account things like income disparity between countries and so on - that is, median income in Bangladesh is very different than the US today, but this was Antebellum south, at a time when America was still a developing country.
All this to say - maybe $4k/year was a "fair price."