Product review (5 stars): Ludicrously expensive for what it is, but it is ...
Ludicrously expensive for what it is, but it is an exact replacement for the original, and installs trivially and works perfectly.  For $20, you'd think you could get a knob machined from billet aircraft aluminum that would never wear out, though. You know what you're paying, though, so it didn't seem fair to take off a star for that.