Well that's some real dodgy use of numbers, right there. In "1 in 4000", "1" is the number of people who died as a result of donating a kidney and "4000" are the number of people who didn't, counted over some sample of living kidney donors.
These two numbers, "1" and "4000" have no obvious relation to the value one places on one's life compared to the lives of others. For example, "4000" is not the number of others lives saved by donating one kidney. By donating one kidney one can "save" one other person's life at most (and it's not really "saving" as it is delaying the inevitable).
Equally dodgy is the calculation of "1/3,000 risk of death in surgery is like sacrificing yourself to save 3,000 people" earlier in the article.
Where does this dodgy statistical thinking (like magical thinking, but with statistics) come from I know not, but, anecdotally it's very common in discussions about doing good with numbers and it seems to be designed to shut down debate by claiming "sciense says".
Btw, if I wanted to know how much I value my life over that of a stranger all I'd have to do is ask myself: how many people would I sacrifice to save my life? I am guessing that for the majority of people on the planet the answer is "0". Simple question, simple answer, and no dodgy "maths".