I don't think there's anything to re-use, is there? All I had left at the end of the quest was a new spell in my spellbook.

Most of the cost is the the first couple of quests in the chain where you have to spend 150g, twice, and 50g on the special horse feed for the DM part of the quest. I don't think there's any part of the expenses that you can skip to get to the end of the quest chain.

Taking extra paladins to the final part in Scholomance would certainly help, though, for the extra stuns on the mobs.