Hollowbone Arrows are only marginally better than Dragonbone Arrows (1 more damage, all other stats are equal), however, their drop rate is extremely low.
In the amount of time it would take to collect a stack of 100 of them, I could easily collect the materials to craft 1000 Dragonbone Arrows, and that is with the acknowledgement that Dragonbone Arrows are already too expensive.
Serpent-man Arrows are only marginally worse than Dragonbone (0.15% less penetration, all other stats are equal).
In the amount of time it would take to collect 100 Hollowbone Arrows, I could easily craft 50000 Serpent-man Arrows instead.
Hollowbone Arrows should have their drop rate doubled at the very least, but making them a guaranteed drop from every Child of Jhil would be even better.
The cost of Dragonbone Arrows could also be reduced, but that’s not the point of this topic…