For many centuries, magical armor has outpaced projectiles in warfare. Armor is enchanted with runes in order to make it more effective, as well as proscribed certain abilities to it. Runes are inscribed into the suit and then placed inside a ritual circle. A mage will then chant the incantation which will fill the runes with aether and activate their power. This spell can take up to 6 hours, depending on how specialized or powerful the suit is to be. Sets of runes, or packages, work together to give the suit its power. These packages can increase strength, speed, resistance to certain attacks, etc.
Runes are generally large and take up a lot of space, which is why they are not found on arrows or bullets. This has given armor the advantage over projectiles for most of history. Recently however, technology has been invented which can inscribe these runes into projectiles. They are made as small as neccessary in order to fit, making them more effective. Then they are enchanted by the mage in the same way as armor. However, having machines inscribe tiny runes onto them is expensive and time consuming. They also have to be enchanted one at a time, and cannot be done in groups. Because of this, they are hard to mass produce.
How can I make design a way to make projectiles cost effective enough to be practical?