Yes, fit is paramount, details are secondary.
In-the-field testing from members of fashion forums show that people on the street are generally unable to identify quality from sight alone, hence the propensity of some labels to provide very large and garish branding. Appropriately, those who I quoted attempt to find articles of better quality without a visible brand name, since symbols like that ruin much of the effect. It also provides a higher barrier to entry, though conforming too closely to community norms can get you labeled "dressed by the internet".
Many of the $1000 items are purchased at much lower prices due to losing "currency" yet still meeting the other attributes. Access to deep discounts like this is only available in-store in major cities (NYC, LA). Ebay is also frequented, along with foreign shops, though with heavy analysis for fakes and by using trust networks and proxy buyers.
Also note that the currency effect happens even for the most common brands - they're following the luxury designers, perhaps behind by a season or two. Why did they have that really nice shirt at J.C Penny last month, but now you can't find it? They don't make it any more, because it was St. John's Bay S/S 10. Check the clearance racks and stick to the classics.
Yes, fit is paramount, details are secondary.
Agree.
Yesterday I attended a meetup where the discussion turned to fashion for a time (because apparently the mini-camp participants were given some instructions on fashion as a useful part of instrumental rationality). (Unfortunately none of us knew much about the topic so the discussion turned into "how can we find an expert to advise us for minimal cost?") It was mentioned that dressing "badly" can be a useful signalling device, and some examples were given. Here's an attempt at a more complete list of possible signals one might be sending by dressing "badly".
The idea here is, if you do decide to start dressing "well", know what you're giving up first. (Of course you're also giving up possibly implying that nobody taught you how to dress and you're not sufficiently strategic to have thought of learning it yourself. Or implying that you don't have the mental, financial, and/or social resources to keep up with fashion. A lot of signaling depends on what your audience already knows about you, or can infer from your other signals.) See also Yvain's related post, Why Real Men Wear Pink and comments there.