The additional costs of the rescue operation are in reality surprisingly low.
The ships, personnel and equipment are maintained 24/7/365 purely for immediate reaction to unscheduled events, be it war or rescue. It was known from the start that there was only 96 hours of air onboard and there was virtually no possibility of saving lives this time.
However, emergency services and the military always react in the same way to such events; spin up the "Play Book" and work the incident through to it's natural conclusion. You may get lucky, or you may not.
Whatever the outcome, the Play Book and all the systems have been tested in real time. Inevitably, there will have been glitches, errors and even things never thought about before, so the next incident gains from those updates to the Play Book.
All the time this operation was in Play, the system remained ready and dealt with other incidents; reality is remorseless and rarely gets these headlines.
The rescue costs won't even appear in any accounts, it is all simply routine operations.