You have to be careful quoting offer prices. Microsoft's 2008 offer for YHOO today would be ~$46.80/share.

It is best to look at market cap to determine value - Microsoft's 2008 offer was $44.6B; Yahoo's current market cap is $41.65B.

The discrepancy from then to now comes from the number of shares outstanding. There are fewer outstanding YHOO shares today than there were in 2008.

Did you also adjust for inflation in there? If not, there's an additional ~10% that can be adjusted for. $44.6B in 2008 would be $49.84B in 2016 USD, an even wider gap.

But there are fewer shares because yahoo "returned" north of $10B to investors through share buybacks. Not exactly sure how that should be accounted for, but I think relevant to the calculation.

Indeed, for a long-term "buy & hold" investor, the share price is much more meaningful than market cap because of the buybacks.

Did that offer include the AliBaba stake?

>YHOO today is trading at $43-44 a share

What % of that is their core business that MS offered to buy?

Yes, for how much now, ~5B. And what are its prospects? It's only been downhill for Y! since then. Marissa did a decent job trying to salvage it after nearly half a dozen CEOs prior to her vacillated, but it just never got its bearing and I fear similar is the case for Twttr.