The mats are not a common drop. And the mats generally come from a total of 6 sources. To fix this i strongly believe making it so that one synth will yield a full stack of 999 arrows, and/or get rid of glue from the synth.
Alchemy: Glue
Ahriman Wing for wing glue, typically you can go some 4+ fights without a single wing dropping. and the lowest level Ahrimans can be is like R36. Ahriman wings sell for 16k on Cornelia server, to make 96 wing glue you will need 8 wings totaling 128k. Then theres the other wings that need to be added, 4x puk wings or 3x imp wings.
Botany: Branches/moko grass/some feathers
Whether its arrowwood or cedar, someone needs to go out there and cut some trees. The yarn needs to come from somewhere right? Start cutting that grass.
Combat classes: Buzzard/cockatrice/vulture feathers.
Bringing the meat home for a plucking. The drop rate of feathers is not as high as it should be, considering that the whole bird is covered with feathers.
Fishing/Mining: Mats for your arrow heads.
From Copper/Tin for bronze, iron ore into iron nuggets. White/Blue/Red Coral, the two colored corals are not an easy catch only common in grade 3+ fishing areas.
Weaver: Feathers into Fletching and Hempen Yarn from moko grass
Fletching difficulty varies with the feather thats used but Vulture Fletching is an R40 synth. Hempen yarn is a low level synth with very limited use, you should be able to find this cheap, but how often do you see it being sold?
Goldsmithing/Blacksmithing: Arrowheads
Someone's gotta carve or hammer out those Arrowheads right?
Carpentry: Making the arrowshaft and the Final Product.
The last step. Having fletching training goes a long way.
The fact that all these parts come from different sources and are made by several different crafts, makes arrows expensive. The only time you will see these cheap if 1 player is doing the gathering and the synthing to all parts by themselves.
The dev's can ease the burden by making 1 synth yield a full stack of 999 arrows. Or get rid of some mats of the synth itself.
please check out my Archer video at http://www.youtube.com/watch?v=9BUeieGTXX4