Begin with direct costs: platform access, model use, tools, data services, storage, queues, and other supplier-backed consumption. Then add operating costs such as implementation, integration maintenance, human review, security oversight, evidence retention, support, and training. Finally, account for exception costs: retries, failed runs, poor inputs, manual correction, customer recovery, and work that produces no accepted outcome.
A provider invoice is useful evidence, but it rarely describes the whole cost of the work. It may show model or infrastructure consumption without identifying the customer, workflow, approval effort, or result associated with that consumption. Finance needs the cost connected to the work unit and period in which it occurred, with unresolved estimates kept separate from reconciled amounts.
A simple formulation is: fully loaded workflow cost equals allocated package cost plus attributable variable usage, external supplier cost, implementation and operating labor, review, evidence, and exception handling. The formula does not create accuracy by itself. Each allocation needs a documented basis, and the company should preserve unknown or shared costs instead of forcing them into false precision.