It mostly goes back to when mortgages (then other debts) were handled by local banks by law, then people in NYC changed those laws so all the money was routed to them. It's not like NYC is just purely more productive, it just found a way to ensure all money must go through them, and they take some of it as almost a form of a new tax. Not that this more central form of banking is all bad, but when almost all the "real" work (farming, building, factories, etc) is done outside the city and they have no real say in the matter it leads to resentment.