Depends on whether you're a professional with accreditation or shooting from the seats.
You actually get very good shots from the press pit/ photographer box/ whatever you call it.
So even a Canon Digital Rebel with a 50mm lens can give good results.
Other than that, it's the photographer, not the camera.
When I shot New York fashion week last year, most professional photographers, over 80 percent were using digital Canon 5D or Canon 1DS With L mid-range Zoom lenses. kit price about $4000 and up.
for runway work I am using the Nikon D 700.
Photos I couldn't have shot a year ago are now possible:
5000 ASA no problem - like 800 ASA on my D2X.
I am also shooting everything in RAW - with a 32GB card I have around 1500 shots.
Attached sample file from a FBI Fashion show - 1/160 @ f 2.8 ISO 2000
I'm currently using a Canon 20D and am desperately seeking an upgrade once I graduate from my university this fall. I love the camera, but the quality just isn't up to par with the newer equipment. Nothing wrong with it, just outdated which is why my upgrade will be a new model in the same product line.
I shoot with a Nikon D3S and a Nikon D700...my main lenses of choice are the 85 1.4, 70-200 2.8 and my 80-200 2.8 AF-S. I did about 70 major fashion shows in 2009. So far I have done about 12 in 2010.