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I think a key part of the question, as I see it, is to formalize the difference between treatment effects and selection effects (in the context where your actions might reflect a selection effect, and we can't make the normally reasonable assumption that our actions result in treatment effects). An oracle could look into the future, find a list of people who will die in the next week, and a list of people who would pay them $1000 if presented with this prompt, and present the prompt to the exclusive or of those two lists. This doesn't give anyone QALYs they wouldn't have had otherwise.
And so I find my intuitions are guided mostly by the identification of the prompter as an "oracle" instead of a "wizard" or "witch." Oracle implies selection effect; wizard or witch implies treatment effect.
Leaving aside lexical questions about the connotations of the word "oracle", I certainly agree that if the entity's accuracy represents a selection effect, then my reasoning doesn't hold.
Indeed, I at least intended to say as much explicitly ("I don't want to fight the hypothetical here, so I'm assuming that the "overall jist" of your description applies: I'm paying $1K for QALYs I would not have had access to without the oracle's offer." ) in my comment.
That said, it's entirely possible that I misread what the point of DanielLC's hypothetical was.