Overall 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.

Luanda is most expensive city to live in the African region, and world-wide, while Asmara in Eritrea is the second most expensive city in Africa (and third most expensive in the world). Kinshasa in the Democratic Republic of the Congo (DRC) is the third most expensive city in Africa.
http://www.xpatulator.com/cost-of-living-article/Africa-Expat-Cost-of-Living-Comparison_711.cfm