Was it really only the maintenance costs?
"What finally killed Concorde wasn't the infamous crash of the Air France Concorde on take-off in 2000, killing 114 people. It was price. Airbus, the Anglo-French joint venture that provided maintenance, told BA and Air France in 2003 it was no longer able to provide support at an economical price."
That is indeed what we were told, but then Branson popped up and said he'd got a contractor ready to provide Concorde maintenance and offered to buy the redundant aircraft - but the airlines wouldn't sell them to him.
Also, Concorde ticket prices were high because its passengers were willing to pay, and many of them were able to pay rather a lot more. Could the airlines really not have paid higher maintenance costs, increased ticket prices to match, and continued to run a profitable supersonic service?
I have a sneaking suspicion that Concorde was taken out of service and retired from flight for reasons more than just maintenance costs. I've nothing to go on myself, no reason to suspect actual skullduggery, and no idea what the behind the scenes picture really was; but maybe one day, the full story will be told.