Earlier quoted context omitted.
You’re forgetting household size. As with all wealthy countries, household size has fallen in Portugal over the past few decades, so the same amount of people needs more house. This is especially true in the context of empty nest retirees.
So that could be one of the extra factors that we're looking for. People want/expect more, which has caused people to have to pay more. But I'm doubtful that it is going to account for a lot of the cost of living issue in Portugal. I'd still like the GP to connect the dots for me on his "it's all demographics" argument. It sounds like are argument you hear on Reddit.
Or, in the case of "world cities" like London, wealthy (nearly all old) people from shaky and shady regimes around the world buy them as places to escape to if need be.
As well as falling household size in occupied dwellings, the proportion of unoccupied dwellings in these cities increases far above the percentage normal for the delays inherent in ordinary buying and selling.
IIRC Paris is attempting to combat this with a surtax on dwellings unoccupied for long periods.