Warren Buffett. AP Images Elon Musk dismissed BYD as a Tesla rival in 2011, ridiculing the design and quality of its vehicles. Warren Buffett's Berkshire Hathaway has made a nearly 40-fold gain on the Chinese automaker's stock. Advertisement Elon Musk laughed out loud at BYD in 2011, three years after Warren Buffett 's Berkshire Hathaway invested in the Chinese electric-vehicle company. Buffett may be the one chuckling now: Berkshire has notched an almost 40-fold gain on its wager so far. "Have you seen their car?" Musk asked derisively in a Bloomberg interview . "I don't think they have a great…