The prices elsewhere is irrelevant. If there is 1 thing that is not movable it's precisely a house. One doesn't buy a building but rather a location. The price of real estate is about the infrastructure available.

Anyway, even if it wasn't about location, location, location (the 1 rule in real estate) here the point is about citizenship, not actual houses. FWIW St Lucia is a beautiful place but... step out of a luxury hotel and see what happens. GDP per capita is low ($15K) and Gini coefficient is high.