Real estate is priced at the margins, because it's rather illiquid. Here's an estimate, there are about 10M people living in Portugal, maybe 5M living in areas (cities, coasts) where wealthy foreigners might want to settle. Average 3 people per household, that's 1.6M homes. Housing vacancy rates in desirable areas are usually 1-3%, so maybe 15-45k available homes at any given time in desirable areas. An influx of a few thousand extra wealthy people (say 3-5k, not just Americans) in a short period of time could certainly have an impact on current vacant housing prices, which might last a good number of years (prices tend to go up quickly, and down slowly).