For work, I wear suits about 95% of the time, and definitely do look at labels when I purchase suits or dress shoes. For dress shoes, I find that the most comfortable and well built shoes are the more expensive - Rockports are my favorite. I've tried "non-label" shoes, and they only last me six months to a year, no matter how well I look after them. My oldest pair of Rockports are nine years and looking better today than the first day I bought them.
For suits, it's not quite as drastic, but I really prefer some labels over others for style of cut, and durability. For example, I have two "Jones New York" suits that pretty much wore out about a year and a half after I purchased. Yet, I have a couple of really nice suits - Hugo Boss, Canali, and one Armani - that have lasted me several years. But, my favorite brand of suit for affordability, style, and durability is Shipley. About 3/4 of my suits are Shipley. Very reasonably priced (you can get on sale for about $300+ Cdn, sometimes even cheaper), nice style, and very durable. My Shipley's are my "day in and day out" suits, and I save my really nice suits for special business functions.
So yes, I do look at labels for my business clothes. I'd rather buy one suit for $400+ that will last me several years if not longer, than buy four $100+ suits that will last me at most two years.