A grounded aircraft is the most expensive aircraft there is. The bill is bigger than the part.
The visible cost
The obvious line item is the component and the labor to fit it. That is real, but it is rarely the largest number. The visible cost is only the part you can see on an invoice.
The invisible cost
The bigger hit is everything the aircraft cannot do while it sits: missed trips, rebooked passengers, repositioning of alternate lift, idle crew, and the reputational cost of a cancelled flight. For a working aircraft, an extra day on the ground can dwarf the parts bill.
AOG cost is measured in time, not just parts. Every hour grounded is an hour of the aircraft's whole value doing nothing.
How to shrink AOG time
Speed comes from sourcing and logistics, not luck. Knowing where a part is, securing it before someone else does, and moving it by the fastest airworthy route is the difference between a same-day fix and a lost week. A desk that works around the clock matters because AOG does not keep office hours.
Documentation matters
A part that arrives without traceability is not a fix — it is a delay. Airworthiness paperwork has to travel with the component so it is accepted at installation, first time. Getting the documentation right is part of getting the aircraft back in the air.