If it costs $900 to make a gadget you sell for $1000 and you replace the staff with robots which cost $500 per gadget then there is no effect on GDP as it only tracks value produced.
The only way to reduce GDP is by lowering the price of your goods (assuming demand stays constant), or implicitly by letting your excess profits sit as cash instead of consuming or reinvesting (which both create and increase value).
The only way to reduce GDP is by lowering the price of your goods (assuming demand stays constant), or implicitly by letting your excess profits sit as cash instead of consuming or reinvesting (which both create and increase value).