Recently, David Merrill, HDS posted his list of 30 types of storage TCO elements. At ANDIROG, I used his white papers, Storage Economics and ROI and Business Case Support for SAN, extensively in business case developments. In my opinion, his list misses the costs associated with replacement, migration, and disposal activities.
Instead of listing TCO elements arbitrarily, I like to divide them in to a grid similar to the picture we used at ANDIROG to explain our focus. Listing infrastructure components and how each one is impacted by infrastructure activities related to customer data highlighting one or two elements from each category with most impact.
It is particularly useful when talking to different IT groups with in an organization or helping one group in selling their projects to other groups.