Luanda is the most expensive city in the world for an expatriate professional migrant to live in 2017, followed by Hong Kong and Singapore.

The top ten most expensive cities in the world comprise two from Africa (Luanda (1); Kinshasa (10)), three from Asia-Pacific (Hong Kong (2); Singapore (3); Tokyo (8)), three from Europe (Zurich (4); Geneva (5); Oslo(7)), and two from America (Hamilton (6); Manhattan NY (9)).
http://www.xpatulator.com/cost-of-living-article/International-City-Cost-of-Living-for-Expatriate-Professional-Migrants_716.cfm