I get your point but none of those are regions with great transit any more. SF's transit is awful, NYC the same. If borderless transit with mainland existed HK'

I get your point but none of those are regions with great transit any more. SF's transit is awful, NYC the same. If borderless transit with mainland existed HK's residential pressure would definitely be eased by Guangdong. Consider Tokyo, where both building and transit have progressed at a good pace and housing prices have remained affordable (despite the fame). Still, maybe I should have put my idea forward a different way: If you are currently facing a housing crisis, the way to fix it is to build great transit to somewhere with plenty of housing availability. This fix needs to be implemented recursively at a scale that matches the city in need. It's much easier than the alternative of trying to densify an existing city, which could be impossible in many scenarios.