Also, deontic concerns about forcing existence on people.

As Apprentice points out the heritability of prosocial behaviors such as cooperativeness, empathy and altruism is 0.5, and I think most people here are aware that IQ has a heritability around that number as well and is a pretty good predictor of life outcomes. If you want to increase the number of people in the world that are like yourself, then having children is a great way of doing so.

I would submit that most people are not very good about judging whether they are prosocial geniuses. (This goes double for people who are likely to be reading this.)

Also: inasmuch as the problem with sperm (and egg) donation is lack at the demand rather than supply end, surely one should seek to enter in on the demand side. Perhaps you really are a prosocial genius, but surely you are not the prosocialest geniusest. You probably suck in other ways too.

Also: heritability is not contribution, but that's veering towards a debate we've had and mostly exhausted already.

Moreover, the people you would save by donating to charity would also have children and those children would have children all of whom might require yet more aid in the future. Thus the short term gains in QALYs that giving to GiveWell recommended charities provides lead to a long term drain of resources and human capital.

That "might" is doing a lot of work here. The overall effect of economic development is to greatly reduce fertility.