@fall19
Sure, it's meaningless to build a small business running on slaves when a basic slave costs as a super car, but we don't really know how much a simple able-bodied slave cost in this setting. We only were told that rare sex slaves are expensive so far. And they can't kill the owner with the collar, so maybe you don't need to spend on guards.
I'm bothered by how incomplete the setting is. Usually slavery is a part of culture that comes with many adjustments to society. For example, counter-ran-away measures. Or more thorough spreading of slavery into society. For some reason, the author stated that slavery isn't common and that doesn't make much sense to me.
I see how naive the author's thoughts are on the subject, I bet he just didn't bother to think things trough.