Ghana seems to be more expensive to live than the Gambia and Senegal.

1 US dollar equals 2.3 cedis
1 US dollar equals 37 dalasi
1 US dollar equals 86 CFA Frac

As of 12/30/2013

Surely it doesn't matter what the exchange rate is but how much things cost in each country. In Ghana for example a cup of American coffee costs 5 cedis i.e. about $2, but what does it cost in the other places?
However saying that if you want to drink coffee, live an expat lifestyle and live in a modern house in an expat area then Ghana is a very expensive place to live!