Why do you think the luxury buildings are a "big issue"? People who can move into those buildings will move into them. This frees up the lower priced apartments they previously (or otherwise would have) inhabited.
I wouldn't make the assumption that the people buying luxury units will be moving out of lower-priced units.
In Canada's major cities, for example, we see such luxury and non-luxury units being bought as stores-of-value by wealthy foreigners trying to avoid risk or capital controls, rather than as something to be actively lived in by them or anyone else. Supply is consumed, without any being relinquished.
Even when the owner might reside in such a unit, it ends up being more like a dedicated hotel room for them. They'll simultaneously own luxury residences in other cities and/or countries, and travel between them. Again, supply is consumed (in multiple markets), without any being relinquished.
The luxury market really isn't like the broader housing market.
Because many are used as vacation homes or just money laundering. With wealth inequality at historical world records, the rich can just buy both, and they do. Lol
