American slavery in the U.S. South was threatened more by the invention of the cotton gin and the global floor for cotton prices dropping. This was diversified away somewhat with Tobacco, but still a major factor in the economics of slavery.
The sad part is that the US South was fearful of this economic reality - up to runaway slaves and illegal slave trade decimating the profit margins - which meant the powder keg for revolt was ready. But as we can see from the Southern "Tax" men stealing from the citizenry, the French less incentivised because of global cotton prices; the future in American slavery was futile.
Just last week, a woman was arrested in Germany for practicing slavery whilst living back in Syria. It shouldn’t be hard to find news about people being sold on WhatsApp in the Middle East. BBC did a special on it. This isn’t even going into the obvious slavery, and the market for it, that persists even further East.
There is a lot of research on this subject but it is worth remembering that slaves were capital that had a price too. So it wasn't "free labour" in any sense.
Most plantation owners didn't end up rich either, there were economies of scale and the price of cotton collapsed over the 19th century.
Over the long-term though, slave labour has typically inhibited economic development.