In the median case, grad school is probably a waste, certainly most PhD's in the humanities are. But with a PhD in economics you can get a job working for all of those interesting sounding NGOs that advertise in the back of The Economist. An MD or PhD in biochemistry/subset is required to do serious medical research.
An MBA from a top tier business school (the more technical the better, personally I'd rather get an MBA from MIT than Penn) dramatically increases salary compared to people without an MBA. Could you have done better laddering up in the corporate world? Maybe, but it's a lot riskier, and the author forgets that pointlessly delaying adulthood is fun! Perhaps the author has forgotten that.
A professional graduate degree also provides you with a risk-free way of transitioning careers. Did you do an undergrad in business? Do you want to program now? Get a master's degree in software engineering.
And the comparison to joining the military is just insulting.