So, how exactly does Beauty Girl Math work? Personally, any time I reuse my hair extensions, I’ve saved money. A $500 human hair wig is less expensive than six $60 wigs. Purchasing a $40 moisturizer at Sephora or Ulta is less costly than a $40 moisturizer from a drugstore. A viral example of Beauty Girl Math is the woman from TikTok who went to Turkey for hair extensions and spent $1,500 on the entire trip. (She was quoted $4,450 by her regular salon in the US, almost $3K in savings.) It’s a hair vacation — and the ultimate in Girl Math. If she and I are Beauty Girl Math-ing, we must all be, right? To answer that question, I spoke to some of the beauty industry’s biggest names to see how they apply Beauty Girl Math to their own lives.