Reylas's Schema for +1 Arrows and +1 Spears
After spending a week in the laboratory and dabbling with eldritch research, you come out of the lab both with the dim glow of a blacklight and a schema that can used to create +1 arrows and +1 spears.
First, in order to enchant each, you must craft each arrowhead or speartip into a geometrically perfect shape. This requires great time and care and even then there isn't a guarantee that the work will be perfect. Forging them from repurposed adamantine steel is more difficult than from raw ingots of adamantine steel.
There is a 75% + Intelligence score of the blacksmith that it is forged correctly. Using repurposed steel lowers this percentage to 50% + Intelligence score. Ten arrowheads requires one day or a spearhead require 1 day of forging. The roll is made at the end of this time and failed attempts are wasted and that material cannot be used in the future (though they are still functional as mundane arrow or spearheads).
Adamantine steel is an alloy of iron (98%), carbon (1.5%), and the magical metal called adamant (.5%). It's value is about 50 gp per lb. Arrowheads require 1 lb of raw material and spearheads require 10 lbs of raw material. Double this amount if using repurposed steel.
Once the heads are forged, they must be bathed in eldritch radiation, formed from high energy consumption of brilliant gems, for one week. Since arrowheads are consumed when fired, they require far less radiation. Arrowheads require 50 gp worth of gems each (usually done in batches of 20 arrows for 1,000 gp). Meanwhile, a spear requires 4,500 gp worth of gems that must be consumed to generate the necessary amount of radiation necessary to imbue the items.
This means a total cost of a +1 arrow is 100 gp each.
The total cost of a +1 spear is 5,000 gp each.