Plenty of people in Hong Kong and Japan live comfortably and happily in apartmetns as small as 300-400 sqft where as in many cities in the west such small apart

Plenty of people in Hong Kong and Japan live comfortably and happily in apartmetns as small as 300-400 sqft where as in many cities in the west such small apartments are not allowed. That's a building code issue. You can't build cheaper housing because of the code. Similarly in many areas house require garages or parking space and front yards of a certain size by law. Again, housing codes dicate whether you can make something cheaper or not.