Lots of humans in the build process. They might have robots making battery packs but all the engineering on those is done and dusted, probably a decade ago.
Generally people don't start building/buying robots to do this stuff until the economics forces it. That probably doesn't happen until they sell a million or more cars per year.
EDIT: This is factually incorrect as Tesla does employ a lot of automation. But there are still plenty of people in the loop as well.
Tesla's factory is fully automated, as automated as any other automobile factory. It is practically impossible to get the necessary level of repeatable precision without it. http://www.teslamotors.com/gallery#
Generally people don't start building/buying robots to do this stuff until the economics forces it. That probably doesn't happen until they sell a million or more cars per year.
EDIT: This is factually incorrect as Tesla does employ a lot of automation. But there are still plenty of people in the loop as well.