I’d personally think of it this way: the difference between a young-adult and an infant dying is that the infant lives for about 20 years, both enjoying their life and costing time/money to raise. The benefit from enjoying life for 20 years is much higher than the cost of raising the child (for a middle-class American, $5-10m vs. $200k), so if I had to estimate, I would say that saving a baby rather than a 20 year old is about 1⁄4 as good as unconditionally saving a baby’s life.
I’d personally think of it this way: the difference between a young-adult and an infant dying is that the infant lives for about 20 years, both enjoying their life and costing time/money to raise. The benefit from enjoying life for 20 years is much higher than the cost of raising the child (for a middle-class American, $5-10m vs. $200k), so if I had to estimate, I would say that saving a baby rather than a 20 year old is about 1⁄4 as good as unconditionally saving a baby’s life.