From what I had read in passing and remember.

  - They were loud (sonic booms were nasty).

  - They were expensive to maintain and operate. Guzzlers. (Britain and France clung to them as a matter of pride/ego)

  - They were narrow and uncomfortable. I have seen videos where there is space only for one stewardess to walk. I had been inside of one in Seattle museum. Very cramped.

  - As you mentioned, ticket cost was high.

  - I suspect people traveled in these mostly for bragging rights.

You made this point in passing, but it's so relevant to LLMs I wanted to highlight it: The development and operational cost was heavily subsidized by the British and French governments, because having an SST was a point of national prestige.