I fail to see how re-taking (or even taking?) the GMAT will close any doors, but whatever.
From my reading and other research I do agree though that once you break a certain threshold you're really better served by keeping your $250 and beefing up your other admissions materials - get someone professional to proof your essays / resume. A 90+ percentile score should be enough to secure a spot, provided the rest of your application is similarly strong.
See :
Class Profiles - MBA - Harvard Business School - most recent entering class had middle 50% range 700-760.
Admission: MBA Program: Stanford GSB - median GMAT of 730.