"If the work that slaves had done was rewarded and paid for"
Because free labor doesn't magnify profits?
The South has always lagged economically since the Colonial Era.
But as you basically referred to, having its economy dependent on two cash crops, which, well good enough for stuck in the pockets of plantation owners, didn't do a heap of good for the rest of the citizenry.
But that was then, this is now, and now says that slavery ended a century and a half ago.
Perhaps it's time to look into branching out a bit more than cotton and tobacco. The Walmart can only doso much, as manufacturing from the North offered tax incentives to move down South has shown.