True, but the point of automation is that the robot can be built and maintained by fewer people than it replaces.

The point is that there's not some arbitrary fixed limit of potential jobs. People pay for what they find valuable, and there's an infinite number of possible things people can find valuable. Furthermore, the more things get automated, the cheaper necessities become, and the more money people will have to spend on things that were previously regarded as too frivolous (there was a time when a calculator was considered too frivolous; now you get five of them for free just by visiting a career fair). People will have to provide those things, which creates new jobs as a direct consequence of old ones being automated out.