Platform-based technology firms are fundamentally different than businesses of the past. By harvesting user data, platforms can accrue monopoly power. As a result, platforms do not generate efficiencies as much as they inflict a variety of quantifiable privacy harms on individuals. Given the relationship between insufficient competition and privacy, I argue that it is troubling that the laws meant to protect consumers from the dangers of uncompetitive markets—i.e., the antitrust laws—are wholly unable to remedy privacy harms. The reason for this blind spot is that consumers enjoy services for free or at a very low cost, even in the absence of robust competition. Indeed, antitrust’s architects likely never foresaw an age in which firms could render anticompetitive effects without charging a price. I argue that antitrust law must modernize to accommodate the real costs of “supracompetitive privacy.”