Update, May 16, 2007: Several correspondents have pointed out that thanks to Major League Baseball's luxury tax, the Clemens signing will cost the Yankees closer to $26 million than $18 million, the latter figure representing his prorated 2007 salary. Strictly by the ledger-book, $26 million is too much to pay for the four wins you'd expect Clemens to add. On the other hand, the same forces that subject the Yankees to the luxury tax mean they may have more to gain from a championship season than Nate Silver's generic formula suggests.