Simply put, it very much depends on the industry.
I wear shorts, a t-shirt, and flip flops everyday to work. And while I am not a CEO, I make a substantial living. Well enough to support two people and enough animals that I've started to lose count.
Fortunately, the edict that you must wear a business suit every day to be a professional has started to drop off, as more companies realize that what a person is wearing does not equal their ability.