Most non-audiophiles have blind faith in the giant audio companies. I wouldn't have become an audiophile if the $99 computer speakers I got at comp USA didn't suck 5 times more than ten year old $5 computer speakers.
Once you realize how horrible most mass-produced headphones are, you know you have no choice but to spend $50+ on headphones not sold at bestbuy. And the reason I have a $300+ headphone is for educational purposes heh heh heh. Honestly though, now that I know what hi-fi tastes like, I wouldn't be too sad if I was only able to keep my $60 portable headphones and mp3 player, musical enjoyment doesn't require that much fidelity.
I'm not sure anyone has asked me about my headphones yet - but if anyone does I'll give them the same answer I give when people ask why I spend £200 on a graphics card or have spent over £2000 on bikes. Because I enjoy it.