and now I bring this thread back from the dead, as I just remembered a campaign I've run where there was a valid explanation as well:
Consider death as a force, or deity unto itself...or perhaps create a deity whose dominion is death. Death is natural, and comes to all creatures, perhaps even the gods. Returning from death to life is an inherently unbalancing event...in fact, I would put forward that in some campaigns you could interpret it as intensely chaotic.
The gods - not just the god of death, have plans and schemes, and generally speaking having death be a minor setback tends to disrupt those schemes (JUST when you thought Mort Spackle was no longer an enemy/asset...).
If you imagine that the main reason the gods have for resisting the return from death is that it injects chaos and messes up their divine plans, then you could see how they would be far more worried about the return of the Great Shempf than they are about the return of Pharmer Phred ("An extra seventeen bushels of lima beans are at that market!!! My plans are ruined!!!").
But of course I still lean toward the economy thing. It just makes sense to me...the only issue with using that rationale that I can see at the moment is if the PC's group is somehow able to bluff the priest into believing that they are all destitute...but maybe inherent in the casting is an understanding of the truth of things.
Maybe it's just all about elk.