Because there isn't enough houses being built, and prices are set by supply/demand, rather than salaries vs. costs of building a house. Looking at it in anothe

Because there isn't enough houses being built, and prices are set by supply/demand, rather than salaries vs. costs of building a house. Looking at it in another way, if you gave every homeowner in the country a lump sum of cash equal to the amount of equity gained through mortgage payments (not including equity gained through appreciation), many/most homeowners would not be able to afford to buy their homes at the current valuation even starting with that lump sum of cash.