Well, they’re really $350 at headphone.com, but yeah, still well above $100. I guess for $100 or so, you’re looking at the Sennheiser HD-280 (which gets okay reviews) or the Grade SR-60 (which is supposed to sound good, but be hideously uncomfortable, as it sits on your ears).
That said, if you can afford it, don’t automatically throw out the idea of spending a lot of money on headphones. I got a pair of HD-580 headphones (now tragically discontinued) for $300, and they gave me sound as good as a $5,000 speaker system and lasted me for ten years (and would have lasted longer if I didn’t get the upgrade bug). Meanwhile, the graphics card I paid $500 for two years ago is already worthless. Headphones are a fairly durable good, and it makes sense to pay for quality, because you get to amortize it out over a long time – plus, dollar for dollar, headphones are a steal for the audio quality you get.