I say we go ahead and declare all fashion shows a kind of performance art that is unrelated to what people - even the ones in the audience - would ever wear anywhere but a runway. It's not fashion, it's clothes as art. Or if you insist on calling it fashion, then there are two types of fashion: what you can wear in public, and what will only ever be worn that one time on that catwalk.
Mokalus of Borg
PS - It doesn't apply to every single fashion show, though.
PPS - I guess that's the main complicating factor.