Many of the expensive properties on the Atlantic Seaboard, if not most, aren't owned by South Africans. Many are owned by UK, German or Dutch citizens, and many spend most of the year empty (which is such a shame). A few years back our government started making it more difficult for foreigners to purchase property in South Africa. The good thing about that is that it prevents our foreign friends from quietly turning Cape Town into a part of Europe ;), but it's bad from the perspective that it reduces foreign investment in the country.
Kind-of a catch 22; don't you think?