Plus there's the initial rather substantial outlay for the machinery and the skilled workers to look after them; the running expenses of spare parts etc.; the diverse problems of fuel logistics, as the stuff has to be shipped in from God knows where at whatever extortionary expense the guys who own the source and the transportation chain manage to wring out - plus the vulnerability of that supply chain, whereas slaves were readily available from numerous sources. Etc.

Fact of the matter is, established elite groups deriving major income from the "latifundia" pattern of economy can generally keep improving their profits for quite a while just by adding more slaves, serfs, ill-paid peons or whatever and squeezing and controlling them harder, and also tend to be rather hostile to anything that might endanger their lucrative position. This seems to have been true for Rome; it certainly was for the Early Modern "new feudalism" that took root in Eastern and Central Europe and much of the Mediterranean zone and quite possibly screwed them six ways to Sunday (with repercussions lasting to this day); as it was for the "Cotton South" of the US, the sugar plantations etc. of Latin America...


Also, KozaK ? Er, no. Not really. You're making some pretty seriously sweeping and unfounded assumptions there.