Like most green items these days, it depends a lot on chance. A lot of folks sell greens they get for a generic 3-5k range. A lot of buyers will expect the same generic range for anything with green text.
Looking at the wiki page for that staff, I'd guess the following
- The stats aren't bad at all, but I'm not sure there's a huge demand for enchanting Smiting Staffs these days. There does always seem to be at least a minor demand for such things.
- The skin (Ghostly, Smiting) is pretty popular, and it's black (also popular)
- It drops from a farmable boss, but not one that folks routinely kill in the current PvE meta
(The point farm in that area uses a quest which makes that boss not spawn.)
Considering all the above, I'd try for 10-15k if I had one to sell and needed a price to list. It's always nice to get stuff cheap if possible, sure, but if I was looking to buy one I wouldn't feel the same range was inappropriate.
If you do sell or buy one, please be sure to let us know on
the green price guide, and I'll update the OP with the data.
Cheers & GL!