You see $12 is still lower than the current expected value of the stock according to at least one analyst report we know off. Morgan Stanley had the current fair value at $13, assuming a low chance of Tysabri back in full.
For example Smith Barney said 60/40 that Tysabri returns I believe?
If we only assume 60% chance of full return and 40% chance of absolutely no return we get an estimate of :
60% * value with T + 40% * value with no T = 60% * $23.16 + 40% * $5 = $15.90 [ value with T based on 200-day average, value without T based on Morgan Stanley estimate ]
The proper way to do it of course is to use a set of scenarios, but this gives the general idea.
But the moment Tysabri is back the estimates will largely come back to the old estimates, toned down a bit probably (a wait & see attitude). But still they are very likely to be at least the 200-day moving average, so about $23.
Now then, if you and I know that and all the analysts and brokerages now that would I, you or they dare to open so low? I for one would simply try to get some at a price between previous (say $13) & then current fair value (say $23), which in that case would be $18.
Of course in the end the opening price will be determined by a specialist, but the average bids & asks is what drives his choice & I think those will be more in the $18 range.
But I agree that the next stop would be the low twenties, unless there is an immediate avalance of upgrades.