There are several ways of measuring the economic wealth of a city. Mostly the basis for measurement is used in comparison with other cities as long as there is a common ground for such comparison.

AfraAsia Bank's Africa Wealth Report 2017 made a comparison of 23 African cities with the highest number of billionaires as at the year 2016. In the list of 23 countries, Lagos, Nigeria's former capital came 4th, only topped by two South-African cities; Johannesburg and Cape Town as well as the Egyptian city of Cairo.

Lagos has 4 billionaires and 360 multi-millionaires.

Below is the list of cities and the number of multi-millionaires they have respectively:
1. Johannesburg (incl. Sandton) - 970
2. Cairo - 480
3. Cape Town - 440
4. Lagos - 360
5. Nairobi - 280
6. Luanda - 240
7. Durban (incl. Umhlanga) - 130
8. Pretoria - 110
9. Casablanca - 110
10. Accra - 100
11. Abidjan - 90
12. Algiers - 90
13. Alexandria - 110
14. Windhoek - 60
15. Dar Es Salaam - 50
16. Gaborone - 50
17. Mombasa - 40
18. Abuja - 40
19. Addis Ababa - 40
20. Kampala - 40
21. Maputo - 40
22. Lusaka - 30
23. Marrakesh - 30
With no other Nigerian cities listed, the nation’s commercial nerve-centre automatically clinches the wealthiest spot among Nigerian major cities. The report is the result of New World Wealth’s extensive research covering the wealth market in Africa which report covers wealth, luxury, prime property, collectable and wealth management trends on the continent from 2006 to 2016, with projections to 2026.

Source: https://www.naij.com/1117200-top-23-african-cities-highest-number-billionaires.html