Graduation rates at universities for the elite are nearly 100%. Getting into the club is the only hard part and everyone involved knows that.
Empirically, what's required to get into the club is being wealthy enough to afford the private schooling, tutoring, and extra circular activities necessary to help your child game the admissions process.
As long as people value these prestigious brands, the elite will continue to buy them for their children. It's got nothing to do with education itself, which could be obtained any number of ways already.