But compared to 3^^^3, it doesn’t matter whether it’s a million people, a billion, or a trillion. You can certainly find a number that is sufficient to sustain an economy and is still vastly smaller than 3^^^3, and you will end up preferring the smaller number for a single additional year of lifespan. Of course, for Rawls, this is a feature, not a bug.
If the economies would be the same, then yes. Don’t fight the hypothetical.
I think “fighting the hypothetical” is justified in cases where the necessary assumptions are misleadingly inaccurate—which I think is the case here.
But compared to 3^^^3, it doesn’t matter whether it’s a million people, a billion, or a trillion. You can certainly find a number that is sufficient to sustain an economy and is still vastly smaller than 3^^^3, and you will end up preferring the smaller number for a single additional year of lifespan. Of course, for Rawls, this is a feature, not a bug.