London also has another problem, non-domiciled residents who only have to pay a flat fee income tax on global income and a non-existent property tax scheme. The combo leads to an explosion of real estate as bank account and very wealthy people moving into the key city of London, making it impossible for even the upper middle class salaried briton to buy property.

You might as well call the entire UK rainy Monaco.

On top of that, the finance types have been there for quite a while, but it's only in the recent few decades that have made london extra crazy.

Other regions of the USA have had economic booms, but it hasn't ended up with hyper growth in property prices because they have less supply restrictions in development.