What is the source (book/page) that identifies how to reduce magic items costs by adding use restrictions. ie, race, alignment, abilities etc?
Example: +1 Bane (giant) shortsword would cost 8310GP.
But if the creator makes it usable only by dwarves it should reduce the price by "X"%. (Believe it can be further reduced by adding Lawful alignment & again by adding knowledge _____ +5 requirements. (I don't know what the % are because I can't find the source.)