Something for nothing? You gave up on that proposition long ago. Cosmetics companies know this, of course. Which is why they’ve mastered the art of giving you something for something. (Free tote with purchase! Free moisturizer sample with toner!) The best of the bunch: Benefit’s new Pretty Parties. Grab 10 to 25 of your best gal pals and head on over to any of the five Benefit boutiques in the evening (i.e. after the store closes to the public). Snack on wine and cheese (provided by the store) and enjoy makeovers, brow arches, brow tinting, lash tinting, face waxing, and lip plumping (for free). The cost? Each person must purchase $50 worth of Benefit products. It’s the perfect way to celebrate a birthday (yes, you can bring cupcakes and champagne), a shower, or to just get ready for a night out with friends. And it sure beats the usual girls’ night out, which leaves you with nothing but a nasty hangover the next day. All for the cost of buying what you probably already need. Or so they’ll have you believe. Benefit Pretty Parties (415-781-8153). To find a Benefit boutique near you, go to benefitcosmetics.com.