Singapore is the most expensive city in the world for an expatriate professional migrant to live in as at January 2019, followed by Hong Kong and Luanda.

1. Singapore (Singapore-Asia-Pacific)
2. Hong Kong (China-Asia-Pacific)
3. Luanda (Angola-Africa)
4. Oslo (Norway-Europe)
5. Zurich (Switzerland-Europe)
6. Hamilton (Bermuda-Americas)
7. Geneva (Switzerland-Europe)
8. Tokyo (Japan-Asia-Pacific)
9. New York (Manhattan) NY (USA-Americas)
10. Monaco (Monaco-Europe)
11. Freetown (Sierra Leone-Africa)
12. San Jose CA (USA-Americas)
13. Bangui (Central African Republic-Africa)
14. Yokohama (Japan-Asia-Pacific)
15. George Town (Cayman Islands-Americas)
16. Copenhagen (Denmark-Europe)
17. Shanghai (China-Asia-Pacific)
18. Nassau (the Bahamas-Americas)
19. San Francisco CA (USA-Americas)
20. Sydney (Australia-Asia-Pacific)
21. Honolulu, HI (USA-Americas)
22. Osaka (Japan-Asia-Pacific)
23. Nagoya (Japan-Asia-Pacific)
24. Kobe (Japan-Asia-Pacific)
25. Macao (China-Asia-Pacific)

https://www.xpatulator.com/cost-of-living-article/International-City-Cost-of-Living-for-Expatriate-Professional-Migrants_716.cfm