I disagree.
I have many high quality headphones and playing competitively with them, yet they all perform differently. Yea, I have a pair of STAX with better soundstaging, had a pair of A2000X with a large soundstage, had a pair of K701 with overblown soundstage, have a pair of AD1000PRM that makes all sound a point source. Yea, does it all matter, it does.
Gaming sound its not all about positioning, one of the main thing that affects immersion is the sound. The most sucess that I have in game is the STAX and the AD1000PRM. The STAX does general direction sound far better but the AD1000PRM is good at pin pointing the source (useful for shooting through visual only obstacles.) To be honest, I found A2000X is better than K701 too and putting K701 and W5000 at the bottom of my list.
How much is worth its all your decision, but does it makes any differences, I say yes. No 'high-end' gaming headset have come close to the hi-fi phones.