The Concord was decommissioned because the fleet was aging and the maintenance costs were rising - including the fact that they got only a flew flights out of the landing gear before the tires had to be replaced.

The Concord crash lead to a lot of stories about the aging fleet and difficulty in getting them properly maintained and serviced, including cannibalization of already dcommissioned planes for working parts, that the customers of the Concord flights lost their trust and started booking slower flights.

It had nothing to do with fuel prices