we're discussing a case where we have no idea what the individual would want and we have to guess
But that already assumes equality of all cases, equality of all wants.
If you say 70% of people would want to live in some scenario, you also have to assume 70% outweighs 30%, which is only true if wants are equal.
But generally, wants arent equal. Being in greatest pain for an hour isnt equal to feeling pleasure for an hour, and these two arent equal in negative want and want.
Wants have degrees, and while most people want to live, most people would rather live in pleasure than constant horrible pain. So even if most would choose to live under constant horrible pain rather than die, degree of that want is generally much lower than living in pleasure.
So even under assumption of same values for pain and pleasure, the case where pleasure doesnt exist, but there exists both pain and pleasure, isnt actually valued same as pleasure, even by most people.
So if we assume 3 persons have negative 10 want for pain (30), and 7 people have positive 10 want for pleasure (70) and arent bothered by pain at all, in case where there is only pain, the 3 persons would still have 30 value, where 7 people would have 0 value (no pleasure achieved).
And when we assume 3 persons have negative 10 want for pain (30) and 7 people have 5 want for life in pain, the 7 people would have 35 points where 3 persons would have 30.
But if we assume some severe pain, the value for 7 people could drop under 5, and in that case, the value of 3 person's wants outweighs value of 7 people's wants.
So it is not just "person wants, person doesnt want", but degrees of wants easily create logical cases where minority outweighs majority.
Even if we assume value of greatest pain and value of greatest pleasure are equal by default, the cases where pain outweighs pleasure in amount would always score in value which doesnt favor pleasure.
And even when we assume most people wouldnt choose to die when under greatest pain, the value of their want would be significantly lower than value of want for greatest pleasure.
So while people who dont want to live under greatest pain can have greatest logical negative value of that want, people who choose to live under greatest pain cannot have even close to greatest value of such want in overwhelming majority of cases.
Again, your case is built on treating all wants as equal in degree, and then selecting majority of wants.
But wants arent equal in degree. Want for life in pleasure isnt equal to want for live in pain, for almost all people.