Concord had a very limited number of viable routes which prevented the program from breaking even with the R&D costs. However, the aircraft was operated profitably later on after significant tick price increases.

A 1 hour US to Asia route that charged 50k a seat could likely be viable. That’s ultra first class, but finding ~100 passengers each way per day should be easy. It’s only expanding to more routes that would be problematic.

PS: The fuel costs would actually be comparable to a regular flight. It’s mostly a question of how many trips the rocket could make and how many passengers it could carry.