I tip my hair dresser heavily, here's why: I don't go very often, and I only go when I'm fed up with my hair, and ready to cut it off. I call her and she will always fit me in within the hour (I don't mind waiting 20 minutes when I get there, that's fine!) ... I usually end up getting either a perm, colouring, or something, so I'm there for at least 2 hours. My perm costs $75, colour is $60 and a cut is an extra 20 (trust me, that 20 is cheap, since I usually only go every 6 months!)
I will easily tip her $50 ... why? because she has never said no to me. Again, I don't mind if I have to wait a bit when I get there, I don't mind if she runs off in between doing things (i.e. to check on other people). I bring a book, and enjoy two hours of silence to read, and walk out with my hair done.
For me, so worth it. In the end, if I actually scheduled 4-5 visits a year, the tip amount would be about the same anyway.