hmmm...
looking at a monosword compared to a sword....
Sword is STR/2+3 with a AP of 0 $350
Monosword is STR/2+3 with a AP of -1 $750
So, Mono arrows would give an addition AP of -1 for twice the cost.
Sounds like a good place to start. and remember the old saiding: "if you can think of it, and would want it. The badguys have thought of it too, and they HAVE it!"