Probably because it is? Have you tried buying a real house in any western country recently? Unless you’re already a milionaire it’s damn near impossible to find anything at a reasonable price.
The taxes are not the problem. The initial cost is.
You can in Denmark borrow 95% of the house/apartment price at very low interest rates. I have a fixed rate 30 year mortgage at 1% interest rate for 80% of my house value, the rest if a loan is needed would be a bit higher.
If you are willing to gamble with a variable rate loan you can get negative rates at the moment.
Houses near metro areas are expensive but outside that they still seem reasonably priced.
I’d say 5x median salary would be reasonable, and maybe a little more.
Where I am, Auckland, it’s about 20x and this is a significant negative.
My experience is in Northern Germany, I heard of even lower prices in the east.