One great reason to refuse that work transfer to Hong Kong: It might cost you an arm and a leg. The city tops Mercer's 2016 Cost of Living Rankings of the world's most expensive cities for expatriates, based on the costs of housing (typically rentals), transportation, currency fluctuation, food, and entertainment, per 24/7 Wall St. The annual survey is pegged at employers trying to figure out expenses for workers living abroad. New York City is the most expensive US city at the No. 11 spot, while San Francisco and Los Angeles come in at No. 26 and 27, respectively. The top 10: