And because the cost of life outside of housing expenses is roughly equal in most parts of the country, housing prices do not scale linearly with growth in median income.
They scale exponentially.
A $6,000 increase in after-tax, take-home pay enables a household to afford the payments on roughly $100,000 more in property value. (Monthly payments, just principal and interest, on a $100,000 mortgage at 4.5% interest comes out to about $500 per month or $6,000 per year.) And, of course, they can make a $6,000 annual increase in rent work too.