that is always something I've wondered about. I always thought the $1.50 bottle of shampoo worked just as well as the $10. One of the chemistry essays in Radar, Hula Hoops, and Playful Pigs, by Dr. Joe Schwarcz is about hair care products and how they work. The section on hair care products was really in depth, talking about the chemicals that actually accomplish the cleaning, and "rejuvenating." He explains why the cheap shampoos will clean hair just as well as the expensive brands. I've got the book loaned out to a friend right now, but when I get it back I will post some of the information. But I recommend going and buying the book yourself, there are about 70 other interesting essays about chemistry's applications in everyday life. Good stuff.