Well i'd assume because most other exotics help during PvE content while the Voidfang are Pvp based, that being said look at things that have been sold recently truth, patience and time, the last word, mida multi tool, mainly pvp based, because of the fact they want to extend game life Pve content must be hard to unlock, whereas Pvp content can never be finished allowing end game items not ruining the excitement of playing