I'd like to point out that the statistical value of human life is used by economists for calculations such as Eliezer mentions, so at some point someone has managed to do the math.
Any mind that I can model sufficiently well to be accurate ceases to be an agent at that point.
If I can predict what you are going to do with 100% certainty, then it doesn't matter what internal processes lead you to take that action. I don't need to see into the black box to predict the action of the machine.
People I know well maintain their agenthood by virtue of the fact that they are sufficiently complex to think in ways I do not.
For these reasons, I rarely attempt to model the mental processes of minds I consider to be stronger than mine (in the rational sense.) Attempting to ask myself what a powerful rationalist would do is not a useful heuristic, as my model of a strong rationalist is not, in itself, stronger than my own understanding of rationalism.