Ammunition +3 and Arrow of Slaying are both classified as Very Rare in the DMG, which according to the Magic Item Rarity table means their value is approximately 5,001-50,000gp. This means that the cost for a quiver of +3 arrows is, at a minimum, 20×5,001 which is 100,000gp. A sword can be re-used an infinite number of times, but ammunition is a one-time use.
What is the explanation for this? Is this is the logical result of game balancing, or is it implied that this ammunition refers to an entire quiver or bag of ammo, rather than a single piece? Or is it simply an oversight on the part of the authors?