Although much has been discussed that cloud computing solutions provide a number of key benefits for enterprises which decide to apply it, however, there is a lack of a certain pattern, which could help enterprises to decide whether the architectural transformation to cloud computing solution will be economically viable. Mathematical calculations and various setting methods of identifying and calculating the costs of applying the cloud is becoming a new challenge. Owing to lack of investigative studies explaining the cost efficiency for business process transformation to cloud computing systems architecture to ensure the economic justification of the transition taken, this paper is to identify the costs of transformation to cloud computing systems architecture, outline cost efficiency method/s, and create a calculation and analytical tool that could be useful for enterprises and decision makers, and use it to assess if transformation to cloud solution was economically beneficial and cost efficient for Riga City Council