correct. Instagram is "worth" $1 Billion to Facebook, but it's worth $100 to a funeral home. But if you think about it, Instagram is worth way more than $1 billion to Google.
Perhaps Instagram should've been worth more than a billion to Google, but that's another discussion.
Google's net income was $9 billion in 2011(http://en.wikipedia.org/wiki/Google). According to Facebook's S-1 filing in February 2012, Facebook's net income for 2011 was... $1 billion(http://www.sec.gov/Archives/edgar/data/1326801/0001193125120...).
The real question still remains: Why is Instagram worth that much to Facebook?