I see this stated all the time on HN, yet there's a whole section at the top of this very comments thread where people are talking about how very profitable the Concorde was.
One person quoted the line "There were times, in fact, when the seven aircraft in the fleet would contribute around 40 per cent of BA’s entire profits."
(the 40% figure is more an indication of BA's sometimes thin margins than massive unfulfilled potential)
If the Concorde had been an actual financial success they would have developed it further and made a successor. And if BA and Air France had thought that the Concorde would continue making them money they wouldn't have retired it after one tragic accident in 30 years of operation. The 737 Max is still being made after much worse.
Which isn't to say Boom may not succeed.