Nightfall skin rarity is still a bit mystery and that's why all I can do is give some tips:
If ancient bows are dropping regulary as white/blue/purple, then I'd imagine this one going for 3-5k~/Salvage.
On the other hand, if this is rare skin (it's at least quite beautiful), I'd keep it for few more days and figure out how rare the skin really is.
Everything is new right now so if I'd give you some exact price estimate, I would just hurt you.
PC Zealous Ancient Shortbow of Enchanting
jackie