> The cost of robots will be zero because robots will mine ore, process it and make other robots.
This assumes, among other things that are unlikely to be true, that the only cost of extraction is (robot) labor, and that mining rights are free, rather than being driven by non-zero demand and finite supply.
(Another critical implicit assumption is that energy is free rather than being driven by non-zero demand and finite supply, as failing that will result in a non-zero price for robot labor even if the materials in the robot were free.)
This assumes, among other things that are unlikely to be true, that the only cost of extraction is (robot) labor, and that mining rights are free, rather than being driven by non-zero demand and finite supply.
(Another critical implicit assumption is that energy is free rather than being driven by non-zero demand and finite supply, as failing that will result in a non-zero price for robot labor even if the materials in the robot were free.)