Have you ever thought about assigning the IT costs in a correct manner? Services and IAM will help you. Services are a means for a more granular view on what IT provides. That is true as well for the IT infrastructure services which are, for example, covered in ITIL. It is true as well for the services used in SOA concepts. But services aren't sufficient. The assignment of IT costs requires the knowledge about the user. Who is using which services in which frequency? This question has to be answered as well. That means, that you have to know in the context of which user a service runs or - more abstract, for infrastructure services - is used.
Thus, bringing IAM and BSM together and combining IAM with SOA is the foundation on which a more efficient IT cost management could be build. And it is, as well, the foundation for the thing I would call ERP for IT.