Humans are still the most flexible source of labor you can use for a task, so it's possible to learn exactly what the requirements are using a human and then try to automate various repetitive parts of the task until the human hardly does anything but verify that the robots are working properly. Note that this does not mean that humans are the least expensive form of labor, although they are currently the only form of labor that can be created by two completely unskilled humans in about 9 months.