She does tho. There are some interviews from 2010 and 2012 saying that she uses Pantene when they ask her what products does she use..
Do you think SELENA GOMEZ uses a $3 dollar shampoo? She uses salon shampoos, the ones that cost like $50 a bottle.
EDIT: She took a picture of her bathroom to explain her beauty rutine. She uses Unite’s U Luxury Shampoo ($43) and Conditioner ($47) and Miss Dior Cherrie along with Britney Spears perfumes.