How much do you tip a hairstylist if they are your friend?

My friend (whom I dance with) is going to be cutting my hair works a high-end salon. He discounts the haircut, but i don't know how to tip him?

generally when a friend is discounting something for you, you should tip them more than you would anyone else, since they are going out of their way to do you a favor and could potentially be putting their job on the line. It really depends on the price of the hair cut. i usually tip about 15-20% same as you would at a restaurant, you should tip him 20% of the undiscounted price.