First of all, the target is not 'below the maintenance cost of the human body'.

The target is 'below the minimum wage that we can pay a human to work for', and that is a very different metric.

Also, as for uptime... The average human performs work at roughly 60% duty cycle. (8 hours sleep, plus meals, bathroom breaks, etc). That is a pitiful number compared to robotics.

Also, when you pay humans at bottom-of-the-barrel prices, they don't have high morale. They are rude to customers. They steal from their employer if they can get away with it. None of these apply to robots.