I am not endorsing slavery by posting this but just talking about economics

The cost of a lifetime slave is very expensive because you pay a lot up front and have to keep the slave in good medical condition to maximize the duration they can work productively

The cost to pay someone per hour is cheaper up front and if they get injured then you can just pay another person per hour and the medical bills do not cost you

Property tax forces employment or jail

Abraham Lincoln made slavery worse

@shortstories I made a similar argument once that the Chinese immigrants out west had it much worse than black slaves did for these reasons.