I mix almost exclusively in headphones....and I use these
I paid like $70...and the mix translates VERY well everywhere...
and they are METAL construction, and built like a tank,
but, again, Headphones are HIGHLY subjective, as it's a combination
of WHO is listening, and KNOWING your headphones, not necessarily
HOW MUCH you pay for Headphones! A GREAT Mix Engineer can
take the cheapest pair of headphones and get a GREAT mix out of them!
WHY? Because he KNOWS what he's doing, and WHAT he is doing it with,
and makes his decisions accordingly!
Just like Zack Wylde can take a "Hello Kitty" Guitar...and you know the rest.
(and, BTW, I'm NOT a great Mix Engineer by ANY stretch of the imagination!)