Who wants open borders? Why, the rich who want to get richer, says the Crimson Reach, but not for the obvious reasons like cheap labor:
Notice that the places with the highest and (to the rest of the country) nominally-shocking house prices tend to all be places in which wealthy people live but with lots of lower-class people, including immigrants, in close proximity. Manhattan. The SF Bay Area. The Washington DC area. In all those places one finds huge disparity and stratification by class and (yes) race, geographically close but distinctly separate. Accordingly, in all those places one sees bidding wars to pay 2-3x to live in Good Location X (with “good schools”, wink) rather than 5-miles-away Bad Location Y.
Who does this help, most of all? The people who already own the “good locations”. Such people have a direct financial stake in making the “bad location” all the more badder so that the “good location” they own, automatically scarce as it is, gets only more valuable and in demand by people fleeing and scared of the “bad locations”.
This is probably less of a factor in Manhattan — all five boroughs are served by the New York City Department of Education, though there will be variations even then — but the same thing happens on a smaller scale in mid-sized metro areas too: if you duplicated a $250k Deer Creek house at, say, 36th and Post, you’d be hard-pressed to get anyone to pay more than $150k for it.