In today's dollars... those slaves were worth $420,000. Each.
Now tell me... how well do you care for something that is worth that kind of money?
Do you send your $400,000 horse to the cheapest vet you can find? Do you put it in the cheapest barn you can build and give it the cheapest food you can find?
In addition to the upfront purchase cost... slaves had to be fed, housed, and cared for. In the south for a long time the owners were obligated to teach the slaves to read so they could read the Bible and be saved. All of this...was very very expensive.
So, Nate's pointing out this meant slavery was on it's way out anyway, and all that bloody murder the North committed against the South can't be justified:
The fact is working conditions in the North were far... far worse than slavery in the South... and even though they were called "free" in the North... they were arguably less free than they were in the South. They worked more, for less, had worse living conditions, and often dealt with the same kind of punishments at work that they got from the cruelest slave masters in the South.
I am imagining what would happen if a slave owner paid $420,000 for me and then had to house, feed, and get me literate enough to read the bible. Would the outcome be better than what the modern school system/academia has managed? I think so. The slave owner has an incentive to make a return on his investment, which is why Nate's right. If you are using slaves for agricultural work, and they cost this much, well, that system isn't going to stand for long. Our current masters seem to have incentive to waste us- and that includes those who might take offense at this post. Just think about the U.S. prison system.
Of course, one could imagine a really dumb slave owner, but this is less likely. He'd have to be able to administrate land, people, and have money coming in- enough for such a purchase to make sense. This means he'd have to be smarter than most city, state, and national governments by default to even make the purchase. He can't take on a lot of debt and use fiat money to hide his incompetence.