I'm watching the Clone Wars series and I've just hit S04E12 in regards to the slavers. I understand; but don't agree with, why slaves exist on earth, but in Star Wars, they have droids. These droids have been shown to be very capable and not necessarily all that expensive to own and operate. They can be programmed to be completely obedient and are easy to repair.
I can understand the idea of slaves for 'other uses' but in these episodes they're being used for manual labor. Reading around it seems wookies were also used as slaves due to their strength, however a droid should be stronger.
If this is the case, why enslave. It would probably cost more to feed and cloth a slave than a droid. Slaves aren't normally obedient nor proficient in any skill and therefor would require additional training, which would be time consuming and even more expensive. When they die the cost of corpse disposal comes into play. If a droid is destroyed it can be cannibalized for parts making it cost effective even when they break, think upgrading a computer. When a computer is upgraded, parts from the older machine can typically be used in the newer machine and will offset the cost. That isn't normally possible with living creatures.
Even if you don't incur a cost obtaining said slaves, the one buying them would. The whole slavery thing doesn't seem cost effective.
Is there a good reason, or is this one of those, evil empire being evil before reason issues?