This form of the question considers the other people's speckings to be held fixed. (What if each is willing to suffer 25 years of torture to spare the other guy 50?)

I didn't say that their preference should be the only criterion, just that it's something to think about. As a practical matter, I do think that not many humans are going to volunteer for 25 years of torture whatever the payoff, except perhaps parents stepping in for their children.

I don't think holding other speckings constant is a bug. If you ask the 3^^^^3 people "should I choose TORTURE or SPECKS", you are basically just delegating the decision to the standard human discounting mechanisms, and likely going to get back SPECKS. That's a quite separate question from "Are you, personally, willing to suffer SPECKS to avoid TORTURE". But perhaps it can be modified a bit, like so: "Are you, personally, willing to suffer SPECKS, given that there will be no TORTURE if, and only if, at least 90% of the population answers yes?"