You know that shopping is merely a means to an end, an exchange of currency for goods, a utilitarian process by which necessary items are acquired. But try telling that to your AmEx bill, which bears the scars of many an exorbitant impulse purchase. (No, dear, a marabou shawl is not tax-deductible.) Billion Dollar Babes can help. The notorious sample sale to end all sample sales, held quarterly in New York and L.A., is finally heading to San Francisco this Saturday. And while it won’t cure your shopping habit, it can make it a little easier on your bank account. On the roster for this weekend: more than 40 designers at up to 80 percent off. Like Petro Zillia, Anja Flint, Catherine Malandrino, Rebecca Taylor, Eberjey, Rock & Republic, Tiffany Alana, and Tree. And when it’s all over, you won’t even have trouble looking your AmEx card in the eye. For more information and to RSVP for this event, go to billiondollarbabes.com. RSVP required.