I would be initially wary of such an item.
The closest thing in core rules are the bracers of archery. The lesser is 5k for a +1 competence bonus to attacks, plus a proficiency benefit. The greater is 25k for a +2 to attacks, a +1 to damage, and the proficiency benefits.
But how can we tell what proportion is what? No good way, but we can assume that attack and damage are equally valuable, that both follow the bonus squared progression, that the proficiency has the same value, and solve.
x*1^2+p=5000
x*2^2+x*1^2+p=25000
The system holds when x=5000, p=0
Clearly, this isn't true (though it was mostly for my amusement anyway) but it does point to the fact that on an item that is primarily used by fighty types, the proficiency benefits aren't worth very much.
So, if the competence bonus to attacks with specific ranged attacks is worth somewhere between 3k and 4k times bonus squared, a +4 item is worth between 48k and 64k. 3k matches up nicely with the amulet of mighty fists, which this is broader in application but narrower in effect than.
So my ballpark would be to make it slotted and price it at 3000 times bonus squared for 48000.
Alternately, you could offer the Rod of Precision (maybe called something slightly different) from Complete Mage, which grants Precise Shot and daily uses to avoid miss chances, and is considerably cheaper.
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gnfnrf