How did that happen? Easy, my life is not based on averages
I had a very low income (way below average) when I bought my house. I was just starting in my career. I've had lots of payrises and promotions (i am a middle manager in a large organisation, however I have no qualifications - nothing special and definitely not a neurosurgeon).
My income has more than tripled since 2002, whereas that house has only doubled.
My point is, as life goes on things become easier...you progress in your profession and your income goes up. Depending on what you do, very rarely will your income be exactly 'average'. Stop looking at averages and look at your situation.