We're getting a bit off topic here, but there are a couple of points that need to be said to be clear on things:
Fuel consumption: When in supersonic cruise, Concorde was actually quite economical; the problem was the huge fuel burn required during take off and while operating at subsonic speeds. The airframe - quite reasonably - was optimised for supersonic flight ( during which phase the engines were running at the same rate as when idling on the ground ).
When Concorde was designed, it was hoped that overland supersonic flight would be permitted. In the event, fears over the intensity of the sonic boom led to this being banned, wwhich meant long subsonic segments of flight at the London and Paris ends of the routes. As it happens, the boom intensity was rather less than feared, but the ban remained in place. There are You Tube clips available of the boom as heard from QE2 in the middle of the Atlantic.
An improved version of Concorde, called Concorde B, was under development which would have reduced subsonic fuel consumption and was in fact going to be applied to the 17th production airframe onwards, but this was cancelled and only 16 production airframes were built.
The end of Concorde:
This had less to do with the Paris crash than a number of other factors.
Firstly, because of the nature of the Concorde operation, a high proportion of the passengers were heavy repeat users from senior positions in business, particularly in the financial sector. Sadly, a high proportion of these regular passengers were lost in the WTC on 11th September 2001; worse - in many cases these people were the only ones in their company who had the seniority to authorise other people in their companies to travel by Concorde. It was a double whammy, and in the subsequent chaos their replacements were unable to gain the authority required.
Secondly, while BA had constantly updated their interiors, AF had not - so while BA's flights were nearly always full, AF were losing passenger volume ( some AF flights reputedly only had half a dozen passengers on board ), a factor not helped by it having been one of their aircraft which crashed. And BA had more operational flexibilty, even to the extent of being able to "step back" the diagrams at both JFK and LHR so that a cancellation was very unlikely. AF had a smaller fleet even before the crash and did not have this flexibility.
There was one other important factor; not long after flights resumed a second AF aircraft was almost lost, near Halifax, and only narrowly managed to make an emergency landing. This is well documented on the web and I see no reason to repeat the details here; it did, however, make AF realise what the damage to their image would be if they had lost this aircraft. Faced with their low passenger volume and tighter margins ( AF had a longer subsonic segment frm Paris than BA did from London ), AF decided to pull out.
Once AF decided to pull out, the full maintenance burden would fall upon BA. Even with their higher passenger volumes, the increase in costs would have been unviable. It did not help that the fleet was reaching the point at which a life extension programme would be neccessary, at considerable cost. So a joint withdrawal from service was announced, albeit reluctantly on BA's part.
BA actually made an operating profit from their Concorde fleet which is generally thought to have been £750 million over the lifetime of the aircraft; AF on the other hand is thought to have always run at a small operating loss, which increased after the return to flight.
Rather than put any more detail on here and take the thread even more off topic, I would suggest researching the details over in the Concorde forum; there is an awful lot of material on this over there.
Meanwhile, to get back on topic, electrifcation - like it or not it is the way forward. Apart from anything else, it is easier to scrub the exhaust of one power station than it is for 100 power cars.
