Incivek will gather sales of 800 million in 2013, 500 million in 2014 and 200 million in 2015.If you assume some trailing sales after, of 100 million for few more year and you add the other HCV compounds in the mix (that I did not account for in my valuation) I see the value of Incivek/HCV platform for $1.8 Billion very possible.
Kalydeco is selling now $250 million/yr in the USA. If you count that the extension into other gating mutations is very very likely, that will double the market in the USA. If you now add Europe, Kalydeco will be selling $750 million to $1 Billion/year sometime in 2016. They have many many years of patent life left, so $5 Billion valuation is very very reasonable.