The way I've described that value of the top MBA programs is in 3 (roughly equally-weighted) categories:
1) The Education: Getting to discuss business concepts with a group of smart, successful folks for 6-9 hours a day is very helpful. Most of the content, I could get from books/ online articles at a fraction of the price, but spending the time in a focused way is actually helpful.
2) The Network: In terms of network, this isn't some vague amorphous thing at Stanford GSB, HBS, or Penn- it's knowing several hundred other folks who are going to be very successful in their careers. This can be useful in sales, fundraising, finding a next job, etc. and DOES have a tangible dollar value.
3) The Rubber Stamp: Having your resume say "Stanford GSB" or "Harvard Business School" does have value to future employers or customers- it de-risks you as you've been validated by a famous institution, and helps THEM to associate with these famous brands.
For the top 3 programs, even though they're VERY expensive (approx $250k in tuition + living expenses, plus at least another $250k in foregone income for most incoming students, for $500k in actual cost+opportunity cost), they're almost certainly worth it.
For middle-/ lower-tier MBA programs, 2) and 3) above aren't NEARLY as valuable, or perhaps don't even exist- is your "network" from Podunk State School MBA actually valuable? For these, the only real value is the actual education, and most students would be better served with an online program or just actually picking up some books/ case studies/ reading online articles.