I go with David, just because I own the Beyerdynamic DT 770 Pro which I paid $159 for on sweetwater. They are closed back and extremely surgical - abit too surgical actually (this is why they popular amongst the youth, I guess.) I've never mixed on them, but I do use them for LIVE monitoring - the my go-to headphones for monitoring.
My everyday listening headphones are the Sennheiser HD 280, I paid $95 for them, and also closed back. They are just enjoyable listening to.