I researched my last bag purchase to death before settling on my Plat5 22". With a coupon posted here last year, I picked my bag up for a song: $275 before S+H.
I do not consider this a "cheap" bag, compared to the Costco/Wal-Mart type bags. However, durability and reliability are a big selling point for me. I want to spend this money once, for the next 10 years, and not have to think about it until the bag is falling apart from years of use.
With my briefcase, I purchased a $200 custom messenger bag. The bag is waterproof, has exceptional organization options, and is extremely durable. It's quite comfortable with 30# of stuff in it (Laptop, netbook, notebook, bric-a-brac, overnight clothes, books, magazines, work files) and quite versatile: I've used it as my day bag on urban vacations many times, as an overnight bag for a weekend with the guys, or as a tote when riding to and from the store on my bicycle.
Like tfar, I buy things once, ride them until they fall apart, and expect them to last many years in the process. The dress shoes on my feet were a $350 pair 6 years ago; they have been resoled once since then. I expect another 3 - 4 years out of them before they will go the way of the dust bin. I used to abhor expensive shoes, but I found myself going through a pair of shoes every 9 months or so before I started buying "better built" shoes.
YMMV, HTH, usual disclaimers.
Cheers,
-Andrew