The bigger drivers are broader and more structural: demand has stayed very strong, while new housing supply has lagged badly. In Barcelona, new building permits have fallen sharply, and local rules such as land reservations for social housing, plus limited available land, have made it harder to add enough new homes. At the same time, rental stock has shrunk a lot in recent years, which means the market has gotten tighter even beyond the tourist-apartment issue.
Short-term rentals are part of the problem because they remove homes from the long-term rental market, but they are not the only reason rents are high. The city also faces slow construction, regulatory friction, and persistent demand in a place where lots of people still want to live. So the approx 10,000 AirBnb-type apartments matter, but they are more of a partial release valve than the main fix.