BP falls another ~12% today. From 04/26/10 BP fell a lot, but so did other oil stocks. Comparing fall in BP to say fall in XOM, BP might have lost another
~ 48Billion in market cap so far.

If we assume worst case of 60-70 billion of liability (per the article in guardian), the stock needs to fall to at least ~25 before it moves into cheap territory (it is 37 today)

Of course, they can somehow fix the well tomorrow, and then today’s price is justified. Stock market is very efficient discounting machine in this case.