Affeman is right.
Graduates of Oxford and Cambridge and educated to "rule" and automatically get a green card into high society.
Being smart, motivated, driven, and lucky are indeed all important factors, but they are not on par with saying "I went to Cambridge" or "I went to Oxford". This automatically opens doors into high earning positions around the world. Many top companies and financial institues will simply not consider applicants who do not come from this background.
Yes there are entrepreneurs and successful people who didnt go to Oxford or Cambridge and went on to achieve great things, but if you took an average of 1000 "oxbridge" students and a 1000 "regular" students you would find a vast disparity in earnings.
There is a gigantic skew depending on your profession. No one is going to pay an Oxford registered nurse 200K a year just because they graduated nursing school from there. Nurses make what they make, no matter where they go to school. A hospital isnt going to pay one nurse 70K and another nurse 200K because they went to Oxford. The same thing with most fields, such as social work, psychology, audiology, speech therapist, pharmacist, teaching, etc. Your salary is your salary, no matter where you go to school. Most organizations have the same pay for the same job title, independent of where you go to school. For example, in my field, as long as your licensed, the state pays the same salary rate for everyone, no matter their educational background.
Now, it may make a difference if your in the business or law or engineering world. Top business or law firms usually pay the big bucks to people who graduate from major universities. They want the best of the best. But its dumb to compare a lawyers wage to a teachers wage. Most lawyers make more than high school teachers.
So, it really all depends on the profession. On the other hand, you can go to a shitty school and flourish in your field and become sought out and paid a lot of money. But I think it the end it really depends what your profession is.