It costs about $2500 to save a life by donating to GiveWell's top charities.

And yes, they publish an absurd amount of data to back this claim up, including a carefully-annotated spreadsheet which you can plug your own assumptions into.

https://www.givewell.org/how-we-work/our-criteria/cost-effec...

It's really hard for me to argue that there's a better way to spend your money.