People who bought before mid 04 don’t want to sell because their cost of ownership is managable and they have nice low tax bills. People who bought after mid 04 cannot afford to sell at a realistic price (so they are fishing for prices that arent realistic, and not having any takers). They will either hang on, if they can afford to, or hand the keys back.
So it’s all up to the banks and the builders. Up until recently, banks and builders could find qualified buyers at retail prices, but that should change now. Both of these groups can afford to drop prices a long way.