It's not only speculation, it's also because some locations are a lot more wanted by many people to live there: right next to a big park, walkable neighbourhood, city amenities nearby but few city problems, no highway audible when sleeping with open window et cetera et cetera. More people want to live in prime locations than prime location housing is available.
The big scam are the insane prices for run down shoebox-apartments in shitty locations.
I'm assuming labour cost is still pretty low in Southern Italy, because in North/Western Europe you can have a kitchen and a bathroom renovated for that money, but no way build an entire house.