Actually, 52 years since he is including 20 years for his wife as well. Comes out to $3846/person/yr in today's dollars if the above calculation is correct, which is considerably lower than what I'd sell myself into slavery for.
But, and this is where it gets really messed up - $4k/person/year is significantly more than current global median income. Last I checked (around 2007), this is about $850/year. (Yeah, if you're reading this website, you are insanely lucky).
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."
