There are four primary benefits to having an MBA education: knowledge, perspective, network, and prestige.
The core knowledge you would acquire at a second- or even third-tier business school is not that different from what you would gain at an elite school. The case studies, textbooks, and lectures are very similar. The biggest difference when comparing highly ranked vs. lower ranked MBA programs in the context of "knowledge" is the caliber of students and faculty who drive analysis and discussion. However, with diligence and determination, you can still gain valuable learning at a good, but not great, business school.
Developing a strategic, deeply global perspective is a huge asset for MBA grads. This comes through the variety of elective courses, academic programs, conferences, guest speakers, etc., available on campus. Higher ranked business schools tend to have more robust offerings. Again, however, if you have the motivation to go beyond your comfort zone, search out prominent alumni, engage in dialogue with top faculty, and create opportunities to grow and develop, you can elevate and expand your perspective, even if you are a student at a less prominent school.
At this point, however, the differences among MBA programs starts to become significant. Relationships with classmates, faculty, and alumni are lifelong assets for an MBA student. These individuals become your allies, resources, experts, investors, partners and friends. It's logical that people who have stronger credentials, broader responsibilities, greater clout, etc., will be more valuable to you over the years. Graduates of top-ranked business schools are recruited by better companies to take on bigger jobs with more visibility. Furthermore, because they've been supported, mentored and befriended by more influential graduates, the affinity and motivation to pay it forward tends to be stronger at top-ranked schools.
Finally, there's prestige. Whether that means impressing those you meet at a cocktail party, giving your family something to brag about, or convincing a banker or investor that you deserve the benefit of the doubt on a major deal, having the name of an elite business school on your resume and business card can be very appealing.
So, as you ponder the possibilities when building your wish list of MBA programs to pursue, scoring them on those four dimensions — knowledge, perspective, network and prestige — will help you prioritize your targets and focus your time and efforts on the places that offer the greatest return on your investment.