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I haven't found it in the rule-book (yet?) but are there any guidelines for what spells cast by NPCs would cost; provided the party has a good rapport with the caster of course and/or belong to the same faith in the case of clerical spells.
Main candidates would be spells like cure disease, remove curse, cure poison etc. for those parties that lack sorcerers that are high enough level to cast them themselves.
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In The Anthropophagi of Xambaala, we established 100 gp per spell level as a rule of thumb. That rate can be negotiated at the referee’s discretion. For another frame of reference, in Vol. III, the cost to hire a priest is 500 gp per level per month.