Sovaldi was acquired by Gilead when they purchased Pharmasset for ~$11B.
As for Sovaldi's cost effectiveness, it's more complicated that looking at liver transplants. Of the millions who have HCV, only a few percent will ever need a liver transplant.
That being said, if you look at what it costs to cure a patient of HCV, Gilead's drug is much more efficacious, so the "cost per cure" is much lower than with older drugs.
As for Sovaldi's cost effectiveness, it's more complicated that looking at liver transplants. Of the millions who have HCV, only a few percent will ever need a liver transplant.
That being said, if you look at what it costs to cure a patient of HCV, Gilead's drug is much more efficacious, so the "cost per cure" is much lower than with older drugs.