The main problem is maxing out to the EE cap is reasonably common at level 10, where if this is the case the wind user is better off with a flat 25 int level 10 staff.
Given it's only specifically useful for wind users, the number of buyers are going to be minimal so unlikely to really see a bidwar.
So it then becomes how much do they really want it.
On the other side of the argument getting anything similar to this is extremely difficult and if they're using a level 10 charm with int/life/mana side mods at the price of not having maxed ee, this is likely to be more powerful than a 25 int staff.
I'd suggest in the regions of 500-1000 is fair myself.