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[0] https://eric.ed.gov/?id=EJ1083795. AFAIT this is from "Journal of Education and Practice", which is a peer-reviewed journal
"What's house X worth?" - Some people might be more willing to trade more money for it than others, and hence inequality ensues. Someone might become a millionaire simply from being in the right place at the right time, and/or buying/selling at the right time.
Or, "What's fair compensation for job X?" - Again different people may value job X differently. Hell, the worst high school teacher I've ever had turned out to be the most highly paid (over $160k a year - 20 years ago). Either it was simply out of generosity, or someone held him in high esteem. If the latter, it definitely wasn't me.
Likewise in education:
"Not everyone can go to university X - who gets to go and who doesn't?" - While a criteria may be used and itself may be objective, which criteria to use it ultimately subject to opinion. In ways, this is sort of similar to Goodhart's law.
"What's a degree from university X worth?" - Again opinion is a factor.
etc. etc...
My parents went from poverty to middle class during my childhood, and I was able to go to college with a reasonable familial safety net to support me as a result. I promptly discovered the joys of chronic depression compounded by undiagnosed ADHD, then failed out, but honestly I feel like it doesn't matter a bit in my day-to-day life.
Meanwhile, my wife and I homeschool/unschool both of our children and are therefore deeply involved in their education. I expect that this will mean that they have man advantages over their peers - if I didn't expect this, I wouldn't have invested so much time and energy into it!