[Pharaoh] treated Abram well for her sake, and Abram acquired sheep and cattle, male and female donkeys, male and female servants, and camels.
Genesis 12:16 (NIV)
The rabbis suggest that Pharaoh fell in love with Sarai so hard that not only did he give her the animals and servants, he gave her one of his daughters (from a concubine), which is how Hagar enters the story in Genesis 16.
They also suggest that he gave her the deed to Goshen.