Originally Posted by vid
The HD 600 is old technology and that old technology is what you pay $400 for. As you say, it really makes no sense - though even $250 is exaggerated.
Newer doesn't always mean better in the world of headphones. That's what I learned from the Stax SR-202, easily outperformed by its own grandfather, the original Normal bias SR-Lambda. (Can't speak for the HD600 or any other Sennheiser set, but the principle of the matter still applies.)
Nowadays, those vintage Lambdas will sell for a good $250-350, depending on condition and whether they include a transformer box or not. I don't recall the original MSRP, but a 1979 headphone design that's been discontinued for newer variants still commanding such a high resale price today speaks volumes about its quality...even though I was told of a time when that wasn't the case and they'd often sell for under $100 because people thought they weren't worth it compared to the later Pro bias variants.
Ultimately, it boils down to what the market thinks things are worth-not just for headphones, but for anything money can buy.
For example, most people will look at a ~$1,000 GTX Titan and think that's way too much money to spend on a single graphics card (myself included), and others will happily buy TWO of them for SLI, maybe even three or four, because they think that extra bit of performance here and now is worth it to them. If they think they can get away with selling products at an inflated price because they know some segment of the market will buy, then they will.