A 1000 sq ft home costs nowhere near $200,000 to build. The land, on the other hand, costs more than that alone in major cities.
You can build apartment buildings 5, 10, 20 or even 80 floors high. The cost of land per apartment can be made quite small by building higher.
There are some actual numbers in this Fannie Mae commentary:
http://www.fanniemae.com/resources/file/research/emma/pdf/MF...
The average costs to build 1-3 and 4-7 story apartment buildings was $192.0/ft^2 in 2017, compared to $233/ft^2 for 8-24 story buildings. I assume the square footage includes common spaces. I don't know if they attempted to control for sample biases (e.g. if taller buildings tend to be build in areas with higher labor costs).
And is approximately the scale of central Paris.