$300,000 a year is $190,000 post-tax.

Assuming 20% down, a $1.7M home would cost somewhere in the range of $8,000 a month after factoring in the mortgage income tax deduction.

That leaves $94,000 a year disposable, which is a lot anywhere. This family can readily get a full-time nanny for the early children years, ensuring no parent needs to take time off.

Now make those salaries for the next 30 years.

Your point is valid in that as you make more money more of it can go to housing because a smaller portion is required for things like food, clothing, gas, transportation, etc.

3x gross income was the conventional rule of thumb but truthfully that was back when interest rates were 7% or so. However, just because you can afford something doesn't mean you should.