An interesting perspective that I heard once is that it was the Fax Machine that killed the Concorde. Before faxes, people (businesses) had to physically transport documents, which meant that for large financial companies in Wall St and the London City the Concorde was a great business tool and worth the expense. When the documents you're carrying enable signing a multi-million business deal in the same day, a £6000 ticket is a completely reasonable business expense.
The fax machine rendered that business need obsolete, and leisure travellers can deal with an extra few hours to cross the Atlantic.