Why Does AWS Cost Explorer Show a Cost Increase After Archera Commitment Purchases

Why does a Guaranteed Commitment, Saving Plan or RI purchase show as a big cost spike on my AWS cost explorer dashboard?

No Upfront commitment costs (GRIs, SPs or RIs) can look a bit strange in the "Unblended Cost" cost explorer view when purchased during a month that is still in progress, as AWS attributes the entire cost of the reservation over the month to the day the reservations were purchased and the account that contains those reservations. For subsequent months, similar behavior will occur where AWS attributes the entire cost of the reservation over the month to the 1st day of the month.

As the month progresses you will see the cost of those commitments be appropriately "spread out" across the days of usage in the "Amortized Cost" view, ultimately resulting in a lower cost for the month as a whole. The "Amortized Cost" view additionally attributes the costs of commitments to the accounts that are using those commitments rather than the account that contain those commitments.