buyers and sellers have a range of values where they are OK transacting, and historically those ranges has tended to overlap at the 30% point more than at, say,

buyers and sellers have a range of values where they are OK transacting, and historically those ranges has tended to overlap at the 30% point more than at, say, the 15% point because of those precedents, taking anything below a "standard" premium opens the door for shareholders suing the board for a breach of their fiduciary duty, arguing they should have waited for a better offer. it's a bit of a self fulfilling prophecy. pay more than 30% and the buyers' shareholders will argue the same which is not to say there aren't 10% or 80% premium transactions, but there's a higher bar to be met before everyone is willing to go outside of the 25-40% premium range (my own numbers)