While I agree that pitching is expensive and that the Sox are trying to keep a stable full of young developing arms, I disagree that Beckett is a $20m premium pitcher. There's only 3 in baseball, as far as I know:
From Cot's:
CC Sabathia, $23,000,000 (2009-15)
Johan Santana, $22,916,667 (2008-13)
Roy Halladay, $20,000,000 (2010-2012) (Assumed)
Beckett simply isn't in this class, is he? Everyone agrees that he's shown glimpses of being just as dominant, but he hasn't put it together as consistently as these guys have.
I think Beckett could make more than Lackey, but not as much as Halladay. $18.5m/yr; I'm calling 5 yrs/$92m. If he doesn't resign now his 2010 should be an interesting contract year for him. If he's going to dominante that will be the year to do it.