I was thinking this the first time, but the idea of paying robots a wage makes no sense. If they don't own themselves, then they don't own their time and labor, which means you'd be paying their owner a wage for any work the robot did. Someone could just tell their robot to go work 24/7 and give the owner all the earnings. Either the robot refuses (violating the ownership contract), or the robot complies (leaving no time to earn their own money).
This makes a robot "buying itself" impossible.