Let's say I'm the king of Sweden, and I take back the power from that annoying parliament. I want to appease my people and show that I will rule in favor of the average Joe and against the big evil corporation. So I cut the personal income tax rate by 10%, and I raise the arbetsgivaravgift rate by 10%.

Unless I also forbid renegotiating salaries, don't you think that after a short amount of time "gross" salaries (effectively salaries net of arbetsgivaravgift) will have adjusted and everything will be the same?

If the worker doesn't earn for all these costs "paid by employer", the company would soon go bust.