http://www.nypost.com/p/sports/yankees/matsui_pettitte_carry_yanks_to_series_tVTcoCAfQiCe91y0K5nhCJ
I make no claim to any sort of expertise in baseball....
But my understanding of the thing is that both the NY and Boston franchises pay some sort of a league penalty imposed on teams which go over some set payroll limit and which is spread out to the other teams in the league and they both view that as a cost of doing business. In other words, the Yankees' first concern in life has to be getting past Boston and vice-versa, and then whoever survives that can worry about penants and WS championships.
There is of course at least one thing worse than spending huge sums of money to come up with world championship athletics and every sports fan in the Washington D.C. region knows what that is, i.e. spending huge sums of money and having nothing whatever to show for it like the Washington dead-skins...