While foreign buyers drive the price up in some price location like Saint-Germains des Pres, le Marais and etc...
They have almost no responsability about the price in the 15th arrondissement and most parts of the city.
The main culprit is the lack of residential buildings under in construction.
Today to have prices under €4,000/m² in a quite centraly area (metro) you need to go in northeastern inner suburbs.