I heartily agree with your assessment.  As I related in a post in the Introductions, Help, and Recommendation sections http://www.head-fi.org/t/707419/recommend-top-sq-open-headphone-for-ipod-not-needing-amp#post_10319214 , I was determined to find an open headphone suitable for my iPod that was better than my HD 598, and I was ready to pay for it.
 
Comparative listening tests against the HiFiMan HE 500, Grado PS 500, HiFiMan HE 6 with ER-6 headphone amp (a $3,000 combination!) left me unable to discern a clear preference for these other headphones, costing up to 20X as much, against the HD 598s.  Differences, yes (though slight) but a preference?  NO.

Thanks, kayandjohn! I do agree, much of audiophile-ism is placebo and preference. Most headphones as they grow more expensive follow the law of diminishing returns. 
 
Thus, that's why when I have the money, in a couple of years when these wonderful cans will have worn out, I'll simply get a Sennheiser HD 600/HifiMan HE-400i or some phone in that price range, an amp a DAC (altogether no more than $800) and be done with it.
 
I'd rather not spend thousands on headphones and amps and DACs that have revealing sound with exceptional clarity and the like. As long as I have a headphone that fits to my needs and values my definition of musicality without becoming too revealing, I'll be happy.

I don't mean to say more expensive phones can't sound far better, but to get their full potential, you'll need good sources, amping, recordings and the like. That can get costly (look at Stax!) and I wouldn't be interested in that and so, I'm drawing the line.
 
Cheers!