It sounds like more of an ASD symptom. Having routines and being unable to break them. I have mild ASD and often wear the same clothes/copies of the same stupid free startup tshirt for no real reason other than subconsciously I hate change. I also really haven't bought new clothes for years due to it being too much change to handle. I do make sure they are clean when I wear them tho!
He did hire a professional -- to design his daily uniform.
http://gawker.com/5848754/steve-jobs-on-why-he-wore-turtlene...
I wear a collared shirt and black pants to work every day, but the shirts are different colours. Frankly, my fashion sense isn't great but I look decent in a nice collated shirt and my wife does have a great sense of style (heck, she makes a dork like me look good, I'm always in awe of this ability - it's like a superpower!) so this makes complete sense to me.
I think these people apply the same principle to many other decision making processes in their lives, not just picking clothes, which is very visible hence everyone talks about. I guess saving on clothes is small but many little things add up quickly.
What it really is, is someone making a statement about how important their decisions are.
Lots of well off people still wear interesting clothing.