Other than just wanting it to work for my own personal glory at this point; I think I Chaos is completely right, it will probably just lead to complaining if the wrong cash amount is handed in since I cannot have the npc give back cash if it was working.
I liked the idea of the NPC charging for his skill to decipher the tome, but I will settle for characters just buying an additional item off an npc that is equivalent to 15g to turn in, in addition to the tome.
That way the characters are still paying, but my quest buddy is doing charity work... he'll get over it
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Thanks a million for the help joligario!