Botswana is an upper-middle-income economy with a freer press and lower corruption than a number of European countries. Their level of corruption is slightly worse than that of France, and way better than most South or East European country (source: https://www.transparency.org/country/#BWA ; http://www.heritage.org/index/country/botswana).

Also, they are one of the largest producers of rough diamonds in the world, so a single stone may be a big deal for the company extracting it, but it means hardly anything to the country.

Africa has some insane level of corruption and poverty, but there are some exceptions (namely, Botswana and Mauritius).