>They still need to be fed though, energy, iron, etc.
But just like humans can help each other, robots could help each other too. This includes digging up various resources, finding means of power generation etc..
If you own a factory, what you see is a big box with input and output, human labor is just an annoying variable, removing it won't turn the entire thing "free".
The owner will still expect to trade the output for something else for his benefit.
I am thinking of a case where governments will own the robots. People will pay some minimal tax to pay for the maintenance of the robots. If other robots can be made to do it, then even that cost is saved.
Government will, among other things, oversee that the needs of the people are well served by these robots.