If one can't make a compelling case to be in a higher "band," and therefore get paid more, then I'm failing to see how they could possibly make the case that they are actually 2x productive.
At most companies I worked for, I'm sure there is 2x-3x difference in "raw" dev productivity, or even 10x once we keep in mind the affects of the correct prioritization and technical solution, but the salary difference is almost always within 50% band. The most productive people could never negotiate 5x salaries.
I'm not saying there would be a 5x, or even 2x, salary. Only that if one cannot even negotiate for oneself, on the basis of some self-perceived productivity disparity, a higher salary (of literally any meaningful magnitude), then it seems quite dubious that such a productivity disparity even exists (especially at the perceived magnitude), given how flawed comparing "raw" productivity often is.
