My understanding was that, even for BA, the Concord was profitable on a cash accounting basis (as in, the tickets more than covered the cost of fuel, salaries, etc.) but not when accounting for a) the depreciation costs of the plane, which were much higher than for an ordinary Boeing or Airbus passenger jet since it was a one-off limited run and there were few spare parts and b) as you said, training new people to fly it, since it was an antiquated plane without a glass cockpit and the skills did not transfer to other planes. That's why it got harder and harder to justify over time until it was shuttered after the fatal crash during the general post-9/11 aviation downturn.