You've got the 1st order effects completely right, but there would be several second-order effects that would undermine this result.
(1) There would be a fall in non-skilled wages, increasing demand for non-skilled labour output.
(2) The reduction in marginal costs would increase supply of the good and reduce its price.
(3) The increased profits earned by the firm/robot inventor would increase demand or saving/consumption of other goods.
(4) The change in relative wages would encourage workers to retrain and switch industries.
In 1850, 60%+ of the American labour force were farmers and over the next 100 years their jobs were automated out of existence by range of more efficient 'robots'. This was no-doubt harmful for many specific farm labourers, but didn't 'screw over the economy'.
(1) There would be a fall in non-skilled wages, increasing demand for non-skilled labour output.
(2) The reduction in marginal costs would increase supply of the good and reduce its price.
(3) The increased profits earned by the firm/robot inventor would increase demand or saving/consumption of other goods.
(4) The change in relative wages would encourage workers to retrain and switch industries.
In 1850, 60%+ of the American labour force were farmers and over the next 100 years their jobs were automated out of existence by range of more efficient 'robots'. This was no-doubt harmful for many specific farm labourers, but didn't 'screw over the economy'.