I suspect all the time he saved by not having to think about what to wear he more than spent in thinking about how to justify wearing the same thing all the time, and writing blog posts about it, etc.

I don't know why Jobs always dressed the same, but it could quite reasonably have been to "brand" his image. He was, after all, the front man image of Apple.

Jobs was famous for controlling every detail of his presentations, it's inconceivable that he would not extend this attention to his dress.