Pathological customers are, by definition, bad. I'm not using the term to mean "a synonym of non-paying customers, poor people, or people enthusiastic about the software."

I have heard from many other software developers, and seen in my own life, that charging more money disproportionately chases them away. I had a major decrease in the number I dealt with just when I went from $25 to $30, while sales went up. It is amazing: charge $5 more, see people suddenly have less hard drive failures, virus infestations, and "bad days". (I called you a dishonest SOB thieving from poor defenseless women when I mistyped my password... because I'm having a bad day, you see.) And it wasn't 20% less, it was closer to 80% less.