With all due respect, and please note I'm as excited as anyone:
The Sox FO didn't "beat" Boras, they didn't "steal" Matsuzaka, and Epstein doesn't deserve kudos for playing "poker"
The posting system, as it is, took away the bulk of Boras' and Matsuzaka's bargaining position. From the Sox perspective, the $51m absolutely is part of the overall cost of acquiring this guy.
And from Matsuzaka's perspective what was his alternative? Go back to Seibu and pitch for whatever he was making before....$3m or so? So $8+m a year for a pitcher that has never pitched in the MLB AND has no leverage to talk to other teams probably is not that bad.
I'd say the Sox were in a stronger negotiating position then most of us thought. The impressive thing, then, is that they (and I mean THEY, the entire FO, not just Theo, because he does not operate autonomously) did not allow themselves to buy into Boras claims that this kid was worth $12-$15m per year, excluding the $51m bid.
I'm psyched, yeah, but I don't view this as a steal..just a nice solid job by the FO.