As the door-opener to a top business school education, the GMAT is the highest “return on investment” component of the admissions process, and you should leverage it! 

Moreover, the return-on-investment (i.e., subsequent career and earnings growth) from top business schools far outweighs that from lesser ones, and exceeds by a factor of 10-100x even the most expensive investment in improving your score.

High quality preparation CAN improve your score dramatically (more than the test-makers will ever admit).

Even if you're a fortunate enough to be a “natural” high-scorer, you can still benefit from professional preparation because a high GMAT score:

• Allows you to "donate" points to a competitive school's GMAT average, making your application that much stronger
• Can help you (sometimes automatically) qualify for a valuable scholarship (many have high, strict GMAT cutoffs), enabling a near-instant return on your investment
• Can help you stand out among your peers for certain high-value post-MBA jobs (e.g., consulting, investment banking)