Most companies trying to do business with the 4 billion people who make up the world’s poor follow a formula long touted by bottom-of-the-pyramid experts: Offer products at extremely low prices and margins, and hope to generate decent profits by selling enormous quantities of them. This “low price, low margin, high volume” model has held sway for more than a decade, largely on the basis of Hindustan Unilever’s success in selling Wheel brand detergent to low-income consumers in India.