Cloud computing allows access to computing resources from a number of providers, who offer multiple pricing strategies for selected product characteristics. The service offerings are becoming increasingly complex, with innovations such as spot markets making service selection more difficult. This paper utilizes a task-oriented approach to examine user requirements expressed as ontology to map requirements to cloud service characteristics to which prices are attached. The methodology described in this paper builds on previous work in semantic cloud service description and pricing of cloud services. The advantages of the approach are that there is a clear methodology for deriving prices for cloud services from multiple service characteristics based on semantic reasoning. Knowledge can be created and mapped across multiple knowledge domains such as requirements engineering, service description and cloud economics. New knowledge can be created by reasoning against ontology.