When it comes to buying beauty products at the drugstore , you generally know what to expect: You walk in, head to the dental-care aisle to get the toothpaste you came in for, then suddenly black out and by the time you come to you're in the checkout line with a basket full of "essentials" you probably don't need. (And forget about shopping online — with all those coupons, you could stock up on enough "essentials" to last you the next decade.)