Luxury/premium properties make the most sense actually: they are not expected to last. When someone spends 200k on a normal 4 bedroom house they expect to live in that house more or less as is for a long time (they often move sooner and may have plans for minor remodeling but no major changes are expected because they can't be afforded). When someone spends $3 million on a large mansion as soon as the ink is dry they call the bulldozer operator (who is already parked outside) to start knocking it down so they can build the mansion they want. In short they are buying location and the cost of the building is a rounding error.

If the ocean goes up - well they just build higher, it isn't a significant expense.