But, you need to take into account people in the US needing to pay for health care, retirement/pension, education, sales tax (although the UK has flat rate vat)

But, you need to take into account people in the US needing to pay for health care, retirement/pension, education, sales tax (although the UK has flat rate vat), tipping, insurance for everything health related especially if it prevents you from working. And house prices in london are like house prices in SF, i.e. not representative of the whole country.