I don't think that these shares are a reflection of the value of the output these companies create (i.e. property assets). The shares only reflect their ability to profit off them. The market is reacting to the fact that these companies may have reduced profits going forward.
I think it's well recognized that house prices are sticky though so they may not be priced accurately for the current climate. It took 2 years after the Tokyo stock exchange crashed for it to have much of an effect on the property market over there.