That's assuming the robot builders have some kind of a monopoly. If anybody can build robots but it only takes 10% of people to do it before we have all the robots we need to do everything then the wages for robot builders will be as low as the wages for anything else, otherwise more people would become robot builders and drive down their wages.

But wages are always relative to prices. If everything is being made by robots that nobody has a monopoly on then everything should be very inexpensive. Having to work for the same nominal wages as you had in 2003 is not that much of a problem if nominal prices are now 5% of what they were then.

The problem comes when you have some kind of corruption or distortion or regulatory compliance costs keeping some prices high (see: housing, education, medicine) even as general wages are flat or decline, or just grow less than those costs.