I've got a feeling that Denon have either got plans for a new line because of the medicore reviews or they are just not selling enough so the prices are getting silly.
I like the new line, the D7100 and D600 is excellent. In the UK the D7100 are about £430 which is in the same price league as the Shure SRH1540.
I swear I am the only one here who likes the D7100! I've seen post saying they sound like a muddy fart cannon that isn't worth $300. I do wonder if they have actually heard the headphone with these comments! The D600 soundscpretty much the same but is a bit sharper/brighter and slightly thinner. Both do have this issues with the soundstage where there is no centre, it's basically really wide left to right. It's not bad though, it's kind of speakers in the corner of the room like.