Most business case development is incremental. That is, the business case focuses on changes—increments to revenues and to costs—that would occur only if a company adopts a proposal. The business case emphasizes the relevant benefits of a proposed decision, including
Larger market share
The business case analysis also emphasizes the relevant costs of the proposal, such as
Additional operating expenses
Losses to existing line of business
A business case does not typically include the costs of doing business as usual, because you generally regard those costs as set. You would incur them whether or not the business case is approved for ...