JB swindled Satan
It has occurred to me that the Devil got cheated by JB, even if Tenacious D lost the rock-off. This is because Satan was about to kill both of them and take them back to Hell. JB's deal was that if Satan won he could "take Kage back to Hell". But if Satan won, wasn't he going to take both of them to Hell?
So even if the Devil wins he gets cheated out of JB,
But maybe that's part of the Demon Code dealing with rock-offs--Satan may need to negotiate terms, which would be a major loophole. By challenging him to a rock-off you're almost guaranteed a better outcome, if he needs to ask you what he gets if he wins, and can't refuse.
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