Earlier quoted context omitted.
By law all new developments are required to have 20% social housing. And google search will show you the extent of corruption and free money that goes hand in hand source: https://www.irishtimes.com/news/politics/law-change-to-make-... Also city councils run a large stock of social housing where tenants pay nothing and live for generations
Literally in the headline of the source you linked states 20% are affordable or social housing, not all social housing. And a ten second google about what "social housing" means as I'm not Irish and don't know, tells me that social housing is not, in fact, free and is instead adjusted rent based on your ability to pay. I suppose it's not impossible that some of it is free, since some people may not be able to pay any…
End result is a broken and inflated marketplace