This whole situation makes me really uncomfortable to be honest.
An argument from compassion (like enwiabe's) will obviously say that $500 is a fair price to pay for a life. That hher children need a mother. But can you imagine what kind of mother she would be? I can't imagine that her children would be much better off having a mother who is seriously addicted to drugs, than not having a mother at all.
If we pay for her - where does it stop? What about those other 7 people on the waiting list? Should we pay for them to go overseas in the hope that there is a matching donor over there? What about those 3 who died last year waiting for a liver transplant? what about that homeless guy I walk past every day on the way to work? What about my next door neighbour who I can see gradually wilting away because she has cancer and two young children to support?
It's an unfortunate fact that despite the UN's decree that all humans are equal, supply and demand requires us to make some difficult decisions.
In my view, for a woman who clearly should have known better, who had a second chance to sort herself out (and don't say she was helpless, she is an adult who would have been perfectly capable of checking herself into rehab), if not for the anonymous donor then for her children, and someone who is ill due to no fault of their own who's been waiting for years for a transplant - this is her problem to deal with.
I think it's her children who are the real victims here. (Speaking of which, why was a drug addict allowed to remain in custody of her children?!)