Need some help with pricing Serpent axe!

Item is: Req 8, 14^50 Serpent Axe (grape).

Yesterday, during a trip to FoW, I got a grape "Serpent Axe" (upload isn't working too well, will edit and post a picture). I was going to just merchant it, being a noobie, but my guild leader said it was worth quite a bit.

The stats are as follows:

Crippling Serpent Axe of Axe Mastery (Purple)
Slashing Dmg 6-28 (Requires 8 Axe Mastery)
Damage +14% (While health is over 50%)
Blade mod: Lengthens Cripple Duration on foes by 33%
Haft mod: Axe Mastery +1 (18% chance while using skills)

Any help would be much appreciated, rather new to the market of super expensive items, and have no idea what it's worth (close friends, GW players say around 1 million, which is crazy!). Thanks again!

not sure if it'll hit one million, but could get 400-500k or so perhaps... post it on high end on here with a s/b of 100k and don't post a b/o and let people bid