The reason people pay is the math works out. Spending $120k to unlock career tracks that include roles that pay $500,000 or more is a pretty straightforward cost-benefit analysis.
My spouse did an MBA at a top school and 15 years out a very large chunk of the class are CEOs of large corporations, founders of private equity firms, etc.
The value is mostly in the signaling and network. Being able to get time with half a dozen CEOs simply because you went to the same school is invaluable.
I don’t know if my MBA program is particularly good. Whilst it’s run by a legitimate institution it’s certainly not a particularly prestigious one. I’d expect that it is in a lot of ways very middle-of-the-road.
One thing it has done is reaffirm my pre-existing vague suspicion that, whilst there are obviously no shortage of formulaic, uninspired, and largely street-dumb MBAs out there, a lot of the hate for those with an MBA that I see in communities like Hacker News is probably misdirected hatred toward the realities of business. Especially given how many people here have grown up in a zero-interest environment where they could bounce from place to place being paid very well to sit around in beanbag chairs thinking about engineering problems whilst the money fairies without fail backed truckload after truckload of cash up to their San Francisco office loading docks.