Not exactly. While slaves don’t need to be paid, they are not free to keep, and there is a limit to what one slave can do in a day. If you are working with high value products, there is also the problem that an unwilling workforce (slaves) has the potential to destroy a lot of value simply due to being uninterested in doing a good job.

If a factory machine can produce more in a day than 10 manual workers and require 1 operator, but if the operator neglects their job the machine gets badly broken, it is far more economically advantageous to have 1 happy, paid worker to run the machine than 5 slaves whose cost is the same as the paid worker doing the job by hand.