You act like the slave-owning elite weren't that- an elite. The majority of slaves were owned by a small minority of the population. Besides which, I don't see why "the expense" of having to take care of a slave's children would even factor into it- either they'd be aborted/killed or sold off at a later date. You act like slave-owners thought of slaves as people, rather than chattel. Also, in a society where slavery is normalized (as it must be, to survive into the modern day), why wouldn't owning a slave be seen as prestigious? Southerners fought the Civil War for the dream of someday owning a slave, or better yet a plantation, even if the majority would never have a chance of having one. As distasteful as it is to think about, they would have thought of owning a slave as being as much of a status symbol as owning a yacht or a fancy car.