People are forgetting the utility factor here.
3600 arrows over the lifetime of a PC might only be 120 GP, but it is also 360 pounds of arrows and it fills up a large wagon.
PCs can go through long stretches through wilderness and dungeons, but the Ranger never ever runs out of arrows.
And of course, by level 15 or so, 4200 GP is pocket change.
The reason it is 9th level is not because of the math of the cost of arrows, but because of the fact that the PC is in high Heroic. He's about to become a Paragon PC where mid-range magical effects like a quiver that never runs out of arrows is expected. He's no longer sticking around the village, he's exploring larger areas. It's the appropriate set of levels for handing out such an item, not the appropriate cost per arrow.
3600 arrows over the lifetime of a PC might only be 120 GP, but it is also 360 pounds of arrows and it fills up a large wagon.
PCs can go through long stretches through wilderness and dungeons, but the Ranger never ever runs out of arrows.
And of course, by level 15 or so, 4200 GP is pocket change.
The reason it is 9th level is not because of the math of the cost of arrows, but because of the fact that the PC is in high Heroic. He's about to become a Paragon PC where mid-range magical effects like a quiver that never runs out of arrows is expected. He's no longer sticking around the village, he's exploring larger areas. It's the appropriate set of levels for handing out such an item, not the appropriate cost per arrow.