Pricing of services, especially in a SOA and Grid environment with contractual relationships gain importance in recent years. For the resource planning, i.e. the allocation and orchestration of existing services, service pricing has a major influence. An orchestrator of services may face various pricing models from different service providers with e.g. long-term or short-term contracts, fixed or variable expenses for service invocation. Price as an important non-functional property of services lacks of a systematic investigation in this context, although it directly affects a service orchestrator's business targets. An appropriate categorization of pricing models is essential for this purpose. This paper proposes a classification of pricing models for services in a SOA environment from a resource planning perspective, i.e. for service selection. Moreover, the impact of different pricing models on service allocation, respectively selection, and further implications for an intermediary, acting as a service orchestrator, are presented.