There's a cost to automating any task: the time spent designing and testing the system. So if it doesn't make economic sense to automate a task, then employment

There's a cost to automating any task: the time spent designing and testing the system. So if it doesn't make economic sense to automate a task, then employment will occur instead. That's true, but the cost of automation is declining. What happens when Watson-like systems are available to the average consumer? What happens when NLP becomes good enough to understand standard English? Eventually the cost of programming a computer will drop below the cost of training a human. What happens then?