I used to be a hairstylist, and a salon co-manager. I personally don't believe, and this is just me, that a percentage of the price of the service should be the deciding factor in tipping. To me, it is just a bad system.
In a restaurant, for instance, I go by the AMOUNT of work that the waitress did for us, rather than the percentage. The waitress doesn't do any more work bringing someone a $5 hamburger than she does bringing the patron a $20 steak dinner.
You can have a simple check for $50 that was steak for two people, or you can have a more difficult check that was also $50, but it involved cheaper meals-but had an appetizer, a split dessert, and a mixed drink for each diner. That waitress should get more of a tip-even though the checks totalled the same-because she did more running around, writing, serving, etc.
Go more along the lines of the amount of time that the stylist took with you, and the work involved. If you go to a discount salon and the haircut is $8.99, the "hip" overpriced stylist across the street who charges $50 a cut is doing the exact same amount of work. If the stylists are both spending 30 minutes with you, etc. then the tip should be the same.
If you get a color service-think about your hair. If it is short and it is all colored one shade, it is a much easier service than doing two shades of foil highlights on someone who has curly hair down to mid-back level.
Go more by the service provided, rather than the price of it.
Also...I don't understand the not tipping of someone just because they own the salon.
I am sure that Miss Manners or Dear Abby or someone made this rule up a long time ago, but I don't get it.