What costs were up? The price of slaves was on a steep upward trend for sure, even with their rapidly growing supply of slaves. That can only indicate that they were increasingly more valuable both as labor, and as a self-replicating investment vehicle.
IF slavery was becoming less profitable, the price of slaves would have been dropping, not rising.
But then again, maybe Lost Cause economics operates in a different universe.
Provision of necessities (housing etc.), deterence and capture of fugitives, cost of acquiring a slave itself.
That can only indicate that they were increasingly more valuable both as labor, and as a self-replicating investment vehicle.
Not necessarily. It could indicate that supply had shifted upward, thus raising the price of a slave for any given level of quantity from where it previously was. It could also indicate that demand for labor was outpacing the supply of one type of labor, in which case a substitute would eventually be sought. Put differently, they were able to buy fewer slaves for the same ammount of money as previously was the case. Since slaves were the labor INPUT to economic production their price is economically considered in production decisions. Production decisions change on any number of circumstances but a common one is substitution. Suppose for example you are a building houses for a living and use concrete bricks, which for some reason are the cheapest types of bricks right now. Also suppose they are the same color gray as any other type of gray bricks and that consumers don't seem to have much of a preference for one or the other - all they care about is getting a brick house as long as its gray. Now suppose that price goes up on gray concrete bricks until they become more expensive than gray ceramic bricks. You have a new house starting that sells for the same price as the old ones and want to get it built as cheaply as possible to reap the most profit. Since the buyer only cares that he gets a gray brick house, do you stick with the more expensive concrete bricks or switch to the cheaper ones?