Luanda is the most expensive city to live in the African region, and world-wide as at July 2018 followed by Bangui in the Central African Republic, 2nd most expensive city in Africa, and 9th most expensive in the world.

African countries are some of the poorest and least developed in the world, with relatively low local cost of living expenses; however the cost of importing and transporting the international standard of goods that expatriates expect to purchase in the cities in this region makes it extremely expensive to maintain the lifestyle that they are used to.
https://www.xpatulator.com/cost-of-living-article/Africa-Expat-Cost-of-Living-Comparison_711.cfm