The end of an Era has come. Magic is broken. New Heroes are needed to face the challenges of the new Age!
Could it be made into a wondrous item usable once per day, week, or month?
Once per day would cost 52,000
We have the money, I say we go for it.
Staff of Greater Dispel Magic at CL 20, 50 charges, 1 charge/use is 90,000 gc.
Do you have to be a spellcaster or have UMD to activate it or can anyone use it?
A staff is a spell trigger item, so Greater Dispel Magic would have to appear on your class’s spell list to use it automatically. You can also fake it with a UMD check.
Banishment might also be handy. It would be the same price as the Greater Dispel staff if we went with CL 20 (which means it could work on up to a creature of 40 HD).