Carrying Costs

AITOOW wonders how much of slavery was inevitable if you think of the payment structure as a draw against commission/salary? How much work was done? How much was it worth? Did it exceed the cost of food and shelter and transportation? I suppose it must have been profitable in the aggregate if it was so pervasive. I wonder how profitable. And what role did the lack of effort contribute to its perceived necessity? How heavy a drag on the hard workers were the loafers? Did those loafers contribute to the enslavement of their cohort? Might ownership found it more profitable to hire "free" men (ie itinerant farmers) if they all worked hard. Like the post war South or feudal economies.