The rental prices in Spain skyrocket. I understand it is easy to blame airbnb flats, but it is usually not the reason. The amount of airbnb flats are too small to really affect the market.

What does affect it, at least in Barcelona, is that there is literally no new apartments being built in the city with constantly growing population.

Nice video with scientific proofs on the topic: https://youtu.be/fwUd3tvfqZE