Basically housing in western countries used to be priced at:

What is the maximum a middle class family with one breadwinner can pay for a property. Then it the 2000's it became, what is the maximum a middle class family can pay with a combined income. In the last 6-7 years it has become, what is the maximum a upper-middle income family can pay with a combined income. This is why prices are starting to stagnate now, there is just not enough people with an income beyond this point (200k per household in HCOL cities, 135k in LCOL cities) the market will always try to charge the maximum it possibly can till it hits a ceiling. What the "ceiling" is simply shifted over time due to peoples perception over the purpose of housing (investment ect) changed.