Why do you think it is inconsistent and unreasonable to choose a measure of productivity that says y=5x is more productive than y=x in terms of real output of y

Why do you think it is inconsistent and unreasonable to choose a measure of productivity that says y=5x is more productive than y=x in terms of real output of y given real input of x? > So if the society is willing to pay nurses n times higher salaries than 20 years before, the value of nurses work has become n times higher, and the productivity has increased n-fold. (minus inflation). How do you disentangle value and inflation? I think that makes your definition incoherent as you just loop back to real output and real productivity to measure those things.