Nowadays, several organisations provide services on the Internet with similar functionality but different price and pricing schemes. Since these services are used in service compositions, the providers of composed services have to face the challenge of managing the services they use, in order to decrease the cost of the service compositions without compromising their quality. Several techniques to compute the cost of service compositions are currently available, but none of them take into account all classes of cost behaviour. This paper proposes an approach to service composition that consists of algorithms and an architecture to support the cost management of service compositions by considering several classes of cost behaviour. We developed a prototype in order to evaluate our approach with experiments that show that it properly supports cost management of service compositions throughout the service composition life-cycle. Our approach is quite promising as it is expected to dramatically improve the cost management of service compositions.