What is appropriate tipping these days at a hair salon..especially when your bill is 150.00 +?

I never know how much to tip..I think I over tip because I have been treating the service as a ';restaurant'; service and tipping 20%..which gets to be super expensive..what is standard practice?What is appropriate tipping these days at a hair salon..especially when your bill is 150.00 +?
Why would your waiter get more of a tip than your hair stylist? You are putting your hair in their hands. I think maybe your over tipping your waiter, not the stylist.