Note: Be the Match is only available for people living in the United States.
Be the Match is a sign-up list for people who would be willing to donate life-saving bone marrow to a compatible patient. The way it works is that once you sign up, you are mailed a swab kit which you rub on the inside of your cheek and send back. Be the Match keeps your data on file, and whenever somebody needs a bone marrow transplant, they scan through their database to find compatible donors. If it's you, you get a call.
The sign-up process takes maybe an hour including the time spent mailing the package. Be the Match estimates that the entire donation process, if it ever occurs, takes 20-30 hours spread out over 4-6 weeks, including phone calls, medical appointments, and the donation itself.
Let's say the average person reading this post can make $25-$50 an hour. That means they are spending the dollar equivalent of $500-$1500 to save one life, in the event that they are called upon to donate. I'm relatively new here, but my understanding is that that's reasonably competitive. It also takes the form of hours instead of dollars, which might make it more viable for some folks (and maybe less viable for others).
You can sign up here. Happy donating!
Note: If you are 45 or older, then there is a $100 registration fee (otherwise, it's free).
Note #2: Down below, user HaukeHillebrandt has pointed out a reason why this might not be as great as it sounds, and user MichaelStJules has pointed out a similar reason (see third bullet point of the linked comment).
I don't get all the downvotes. Even if this turns out to not be very cost-effective (although maybe the post should be edited to highlight the initially missed considerations), it is helpful for us to see why as something to learn from.
It also makes the forum seem unfriendly to newcomers.
The post was in the negative for a bit, I think the day that it was posted or maybe the next day.