Watching what you eat gets more important as you get older. When I was 22, I regularly ate 6000 calories + a day, and never gained weight. Now, well...
I don't think he's being an asshat there. I may not agree with his impressions of ultrasone headphones, but saying he things they're flat compared with studio monitors that have been eq'd flat isn't an asshat thing to say.
Offer him less, if he wants to sell it to you he will. Sure, the market is impacted by high water marks, but if he can't find a buyer willing to spend that, he'll get less, or won't sell. It's just a pair of headphones. If they're worth the asking price to you, buy them, if not don't.
What's your agenda? You knew posting internals pictures over there would result in them getting deleted, and now you come over here to talk about it like you're surprised at the reaction.
you could reply and say "oops, I was wrong, here's the right info", and then you're not pretending you didn't fuck up. Your choice. Go the fuck away, or accept that everyone will know you're not perfect.