I pay $50 for the cut, and I tip $10 or $20. Usually it's $20, which is probably overtipping a bit, but the stylist is someone who has been cutting my hair for a long time and who I regard as a friend. I once asked her whether people customarily tip the shampoo-ers. (This was early on in our "relationship", when I had little experience with haircuts not done at Supercuts or a ramshackle barber shop.) She told me that she always shares her tips with them (much as a server may share tips with busboys). Given that, I don't separately tip them.