Wall Street suffered a sharp selloff as investors grew increasingly nervous about the staggering costs of the global AI race. The Nasdaq plunged nearly 1.4%, while the S&P 500 and Dow Jones also ended lower as traders reassessed whether Big Tech's massive AI spending plans can deliver returns quickly enough. Amazon fell nearly 5% during regular trading and slid even further after hours after warning of weaker-than-expected holiday-quarter revenue.