I suspect that you are overestimating how many people are going to be saved by organ donations from a given individual. A single person is only compatible with certain people. A fair number of the people who die waiting for organ donation are not getting donations in part because of a lack of a compatible donor. You may not be adding substantial compatible donors, especially if you are of a common genetic compliment. Moreover, many (although certainly not all) people who are getting organ donations have other problems, so one needs to ask how much lifespan one is actually extending them by.
I suspect that you are overestimating how many people are going to be saved by organ donations from a given individual. A single person is only compatible with certain people. A fair number of the people who die waiting for organ donation are not getting donations in part because of a lack of a compatible donor. You may not be adding substantial compatible donors, especially if you are of a common genetic compliment. Moreover, many (although certainly not all) people who are getting organ donations have other problems, so one needs to ask how much lifespan one is actually extending them by.
http://stanmed.stanford.edu/2011spring/article5.html suggests 11% of donors actually end up donating, and that this is rising rather fast (was 1% as of 1995, up to 11% in 2008)