I've seen them being sold for 5-15m on a number of different shards so far, but its really difficult to give an accurate price on them as more and more will spawn the longer the event lasts. It's also quite possible that the 3 new event artifacts will be added to Doom, or to the Anti-Virtue dungeons.
Lets all be honest though as a weapon its a poor version of a Blackthorn's kryss...so the only real difference is ssi, weapon speed, damage, and how many hands you have to use.