Design vs engineering and costs at Apple

An amazing story about Apple design is that if Jonathan Ive would have added 2mm to a particular design, Apple could have used a much cheaper 3.5" hard drive instead of the more expensive 2.5" drive. (I don't remember the specific product, but with that size, I assume it was an early iPod.) I can see where that would have driven an engineer crazy, but I think you have to look at it as who's in charge at Apple. As an engineer -- or anyone concerned with costs and competition -- you have to state your case about the 3.5" drive, but when you lose the argument, you have to let it go. (There's a little Zen in the letting-go part.)