OK, well, I'm being entirely honest here -- though, obviously, I have no way of providing proof, so it's meaningless to anyone who is disinclined to believe me.
I did go to Oxford, and I went to Oxford as a working-class kid from a school that barely had anyone go to university (this was in the 1990s), far less Oxbridge. It can be done. I'm not brilliant and I was chippy and intimidated at the interview. I was also stubborn and very interested in my subject, and they took a punt on me. I have four degrees, all funded on scholarships. I earned just over 100k last year (not living in the UK, so am translating euros into sterling), though it varies annually as part of my income is variable. I have one child who is clever (but lazy), and still in primary, so no significant exam results as 'proof'. DH has a big job, and earns far more than I do, but does all the cooking and shopping, and a lot of the drop-offs and pick-ups/general parenting stuff, because why wouldn't he? I am deeply normal, in no way the most successful of my friends, not a 'perfect parent', don't have a 'perfect marriage', and I don't 'have my shit together' to any extent. I was raped as a child, and I'm in therapy dealing with stuff that still affects me as a result. A lot of my life in general is complex and messy.
It's not about whether you believe me or not, because obviously, we're strangers on the internet, and I could be anyone!
But what is interesting is the desire to disbelieve this stuff. I mean, feel free to think I'm making this up, but why be so invested in disbelieving it? Does someone else earning 100k really make you feel worse about yourself to the point where you really want to think people are inventing salaries, because it's that incredible?