So Yahoo without Alibaba is worth about $4.6 billion (18.8-14.2), subtract the $2.1 billion cash and short term investments and you get a price tag of $2.5 billion for all of Yahoo's other operations and assets.
And the value of the other Asian Yahoo properties that are fully owned by Yahoo. Yahoo! Taiwan is by far the most visited site in the country, for example. Well ahead of both Facebook and Google. Same goes for Hong Kong. Obviously smaller markets, but one has to wonder what Yahoo! Taiwan/Hong Kong would be worth as a standalone company. It seems to me that would easily be $2B for just that part. Add that to Yahoo! Japan and Yahoo US is valued at some large negative number.