175/35 dex helm on the AH is struggling majorly to sell for 1.5m, so use that as a base. The dex is really nice, it's just the helm lacks a socket which for me can depreciate it quite a bit, though definitely has a bit of value.
The third helm is probably more valuable it's just again, lacking a socket means it lacks x% Life or whatever people prefer, and the exploding palm is so niché that finding this on the AH would be pretty hard.
That dex on the Nat Gaze is nice, and that fear chance is insanely high. It is a great roll, which will you net you probably atleast 3m (similar dex Gazes) though I'm curious to see how much that armour and fear may push up the value. Armour I personally think isn't all that important with the way that people play their DH these days. Who knows how this helm might go up or down in value concerning 1.03.