Tou need to luck at marginal cost: An old person is going to die, 100% chance, and that will cause sadness, etc. The question is what is the marginal value in each extra year of life, not is the death itself undesirable.
But you touch on a deeper question also: "saving lives" is a very modern idea. Traditionally, death was quote common all all corners of society, and the solution was to make more new people.
Your question also touches on abortion, and the argument that a fetus deserves less protection from society because of its lack of social connection. http://www.equip.org/article/steven-pinkers-evolutionary-exp...
But you touch on a deeper question also: "saving lives" is a very modern idea. Traditionally, death was quote common all all corners of society, and the solution was to make more new people.