Spoilers a bit
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ehh scratch that, there's more spoilers here already then I will give..
In any case, while 5K gp is not a big amount, there's no way in Nine Hells I will pay to some Cowled Fools for casting some spells. I simply kill them all and case closed. And without a Sorcerer char, killed them last time with my berserker (and his party) and this time will do it with a Cavalier. I don't play men in dresses, real men wear plate mail
So yeah, kill 'em all. And they do not have the Staff of the Magi. They have their papers, rocks and sticks. OK, scrolls, gems and sticks.