To add to what I think have been many other good comments, in my experience the productivity differentials between individuals in the same job can easily be vastly greater than the upper and lower bounds of that job's payscale.

I can recount cases where I've worked with relatively new engineers (a couple years out of college) who were easily 3-4x as productive as some of their peers. Of course, the pay scale for "Software Engineer" usually only has a band width of about 15-20%. Yes, the better programmer would get promoted faster, but still I've nearly always seen that there is more variance in "creative"-type jobs than pay scales will allow.

So for these types of jobs, posting a payscale is nearly always a bad idea, because it can further compress what is already a "too compressed" payscale.