NEGOTIATING
In the Gambia most prices are not fixed, except maybe in restaurants, hotels, bars, tourist sights and supermarkets. So you will have to negotiate your price. Bare in mind that what would seem a reasonable price for you could in fact be very well an extremely high price for local standards.
As a guideline you should end up paying approximately 40 to 50% of the initial price. Negotiating or bargaining is seen as a social event where buyer and seller try out each others skills and also get to know each other a little.
Strategy and patience will take you far.