Medical decisions in the USA suggest that the statistical value of a “quality-adjusted life year” is ~$128,000 on average. Obviously the question of “life years” is critical in this context. Everyone would be in favor of sacrificing more to save healthy children than people who are 80+. (No one wants to see anyone die needlessly, but the children can live happy lives for another half-century.)
That's the value of an average life. Health economists at e.g. the NHS actually use https://en.wikipedia.org/wiki/Quality-adjusted_life_year, to account for the fact that e.g. an 80 year old has fewer years of life left than a 10 year old.
About zero, really. Unless some of those 80+ year olds are prominent scientists, etc.
The numeric value $1 billion means $1 billion worth of human labor or energy. The amount of this energy is finite, and it's around $80 trillions currently. We can multiply it by 10-100, the exact number doesn't matter, what maters is that it's not a lot bigger than $1 billion. Saying that saving a human life is worth any dollar amount, is same as saying that our society, all 7-something billion people, should spend all their energy on saving that one life.
A human body is really just a vehicle, like a car. When it approaches 80 yo mark, it's worth about nothing. It's just some people believe, with religious rigor, that they're bound to this car forever.
$500m? $1b? $100b?
Just for comparison about 80 young Australians died from suicide this week alone.