It's been noted that apartment developments in capital cities have lead to an over supply but that is a market segment of it's own. When apartments get to the point of over supply developers stop building them, once the supply gets taken up they start building them again.
The supply of stand alone properties closer to the CBD is fixed and due to developers picking them off the supply is decreased, hence up wards price pressure.
And as has happen in the past, what where once outer fringe suburbs are now inner city suburbs.
Have to remember that it is land that has value and that can be increased in value if you add improvements but once you build an apartment block on it the scope for increase in value is much more limited
