The cost of high-speed international connections -- Africa loses

Telegeography, a market research firm, compiles a database of wholesale Internet prices -- the prices a global organization or an ISP would pay. This chart shows a few price examples:

The price differences are dramatic -- a 2 Mbps link between London and Johannesburg costs roughly the same as a 10 Gbps link between London and New York.

A recent New York Times article points out that the cost of serving Web content over slow, unreliable links in developing nations is high and the income from advertising is low. This has led some companies to block developing nations from their sites or to offer degraded content by, for example, compressing video or serving "light" versions of pages.

What are some of the causes of high international link prices in developing nations? What other factors contribute to the Internet being relatively slow and expensive in developing nations?