A 747 carries 500 passengers, Concorde carried 100. Your costs per seat mile are going to be at least 5x higher.
The Concorde engine was efficient at cruise - and pretty awful everywhere else. At cruise it was about 10% more efficient than a GE90. But the Concorde had 4 of them, and a 777 has 2 GE90s.
This is also why you don't see 4 engined planes anymore, except for the A380 and most people were hell bent on retiring during the pandemic until they couldn't get more 787s/A350s and the 777X is delayed.
The Concorde engine was efficient at cruise - and pretty awful everywhere else. At cruise it was about 10% more efficient than a GE90. But the Concorde had 4 of them, and a 777 has 2 GE90s.
This is also why you don't see 4 engined planes anymore, except for the A380 and most people were hell bent on retiring during the pandemic until they couldn't get more 787s/A350s and the 777X is delayed.