The weapon itself, minus the deathstrike bit, would be 128,000 gp. Assuming it takes a 9th-level spell to get the deathstrike effect, three times per day, that would be
9*17*2000*1.5 - 40% = 275,400 gp. However, that's assuming activating the ability would be a standard action.
Now, quickening this bad boy would put it into the epic realm (though it is already), so how about this little nugget. Paying for haste (forget what version, it isn't important) with the straight formula of
3*5*2000*1.5 gives you 45,000 gp. Essentially, this could cover the free action activation. It's something that I've been kicking around in my head for a little while, and it could be used for multiple abilities. For each additional ability that can be activated as a free action, you just apply the cost of it again (in this case, another 45,000 gp).
However, that means you have two additional powers. If you follow what the Sage ruled about additional powers, the deathstrike effect would be multiplied by 2 instead of by 1.5, and any others would be multiplied by 1.5. So, deathstrike would then be
9*17*2000*2 - 40% = 367,200 gp. When added to the free action activation of the deathstrike ability, that would be a total of 412,200 gp for the deathstrike ability.
Adding that to the cost of the weapon, and you get 540,200 gp. I don't remember what the cost for a mighty (+2) masterwork composite longbow is, so I didn't bother putting that in the total. Anyways, something tells me that's a bit high, but hey.
Anyway, if you don't think a 9th-level spell is appropriate to reproduce this effect, just substitute a lower-level spell and redo the math. Personally, I think the above cost is appropriate for the ability, especially when taking into account that activating it is a free action.
Now, I should mention that I compared this to the Bow of the Solars on page 102 of the A&EG, and I can only come to the conclusion that the price of the bow of the solars is way to frickin low.
I also compared your bow to the price of a Greater Slaying Arrow, but just keep in mind that while that arrow is relatively cheap, it's also extremely limited in function.
What do you think?
