DoorDash CEO Tony Xu worried that the added costs of food delivery would scare off Taco Bell customers. Joe Raedle/Getty Images Food delivery has gotten more expensive over the past decade, but people keep ordering. Even DoorDash CEO Tony Xu was skeptical that the extra cost of fast food delivery would work. Customers are paying up for delivery because of the time they save, he said. DoorDash CEO Tony Xu never expected that people would pay as much as they do for food delivery. The delivery...