You are either a foreigner or a young person who did not know the housing policies, cooling measures and what not that the gahmen has imposed on property ownership here.

Another thing you revealed about yourself is that you probably haven't started working or just starting off. If you understood Maslow's hierarchy of needs, you will know that smaller HDB flats (the new 4 room flats and below) will satisfy only the basic needs. As people become wealthier they want to upgrade their quality of life. This desire to want to improve their station in life provides the motivation to people to work harder and earn more.

People with $470k and $700k income pa are already high up in the hierarchy of needs. They are seeking something else, not things to satisfy their basic housing needs. Their main concern would be to build up robust and persistent passive income streams that will enable them to retire in comfort. And if not for the gahmen housing policies and rules, yes these wealthier people would go and buy the HDB flats big and small - not to live in them but to rent them out for passive incomes! Some lucky ones managed to do this before the gahmen imposed the rules blocking out private property owners from buying HDB flats whether new or resale. The result is that these private property owners ended buying more private properties.