Amortized, blended, and unblended cost

Unblended cost is the simplest: the actual rate charged for each individual resource, with no averaging. Blended cost averages a rate across all usage of a resource type within a consolidated billing family. That's useful for a single effective per-unit rate across accounts, but it can mask which specific account or team is driving spend.

Amortized cost solves a different problem: a one-time or upfront commitment payment (buying a reserved instance for cash upfront, say) gets spread evenly across every day of the term it covers, so a single normalized daily number reflects the discount's ongoing value instead of showing one enormous spike on the purchase date and zero afterward. Most cost-monitoring tools default to amortized because it's the view that matches how the discount pays off over time.