Using the Tencent (TCEHY) trailing P/E ratio of 35x, Alibaba Group is worth $80 billion.
Using the Facebook (FB) forward P/E ratio of 36x, Alibaba Group is worth $128 billion.
Using the eBay (EBAY) trailing P/E ratio of 29x, Alibaba Group is worth $66 billion.
Of these three, I think the most relevant is Tencent which is still the biggest Chinese Internet company still experiencing rapid growth – albeit at a slightly slower pace than Alibaba. (Tencent did $1.88 billion in the last year and is currently valued at $65 billion.)
This analysis suggests the most likely outcome is that, if Alibaba IPOs this year (which seems likely), it will be valued at $80 billion.
Yahoo’s 20% stake will be worth $16 billion pre-tax and $11 billion after tax. Using the current share count (which is going to go down with buybacks), it suggests Alibaba alone is worth $10 / share.