Overworking employees have always been one of the things that a lot of businesses tend to do. With robots they can finally do it. It is like the rebirth of the industrial era where machines were first introduced except this time more jobs that used to be only done by humans can be now done by basically much more sophisticated machines.
You are right about the fact that machines can work way more than humans and they tend to do the same work that humans do more efficiently and accurately, however, I'm not sure about cutting costs by replacing humans with machines because their maintenance might cost more than the average salary of an employee doing the same work. In case one of them or some of them gets out of order and requires replacement or repair, it might cost a fortune to the company while if it's a human that needs to be replaced, the company hires another worker without spending any money.
There is no doubt that robots will replace humans in a lot of places and take their jobs, but there will always be other opportunities and positions for humans to take that robots can't do. So humans that think they are doing jobs that can easily be done by a robot or a machine should think of upgrading their skills or learning some other skill in the mean time.