You're assuming that we're at capacity on spending, but we're not. Instead, we can afford to bring 11 individuals into the world. The absolute gain to society is still greater than simply bringing 10 into the world.
Maximizing number of total person years is not sufficient because a population 100x as large but living 1/5 as long would be superior to a population of the current size but living twice as long.
I'd argue in favor of maximizing population size and average lifespan. Of course this ultimately leads to the requirement that humanity moves off of this little rock of ours.
Given X amount of money paid per person as a in premium and Y number of people paying those premiums, we should have XY available to spend on healthcare. That is a hard cap on healthcare spending.
While we can afford to maintain* 11 individuals in the world. There reaches a point where over that entire population, we need to triage the medical issues in that population into the people whose issues maximize human-hours-lived given the X*Y healthcare dollars available to spend treating those issues. Maybe it's not the first person that requires treatment costing a million dollars we need to triage, but you eventually will run out of money if you don't triage because we simply don't pay unlimited premiums to meet the unlimited demand for healthcare.
The issue about overpopulation is a red herring, and in this case isn't just of function of helping people live longer. Many countries once they reach a level of prosperity stop having children at the necessary replacement rate of 2.1 children per couple once that society becomes affluent. The dropping replacement rate often correlates with societies ability to spend more money on helping their population live longer through spending on medical treatment.
Maximizing number of total person years is not sufficient because a population 100x as large but living 1/5 as long would be superior to a population of the current size but living twice as long.
I'd argue in favor of maximizing population size and average lifespan. Of course this ultimately leads to the requirement that humanity moves off of this little rock of ours.