Mick, Concorde was profitable to its operators right up to its final flight(British Airways and Air France) because all the development costs were borne by the British and French Governments unlike the normal cost of a new aircraft where development costs are included in the purchase price.
A survey of the general public by HM government as to how expensive they thought a return flight ticket on Concorde from London Heathrow to New York Kennedy and return grossly overestimated the price so with that knowledge BA and Air France inflated their prices,
There were a number of reasons for the cancellation of the Aircraft.
The American Government refused to allow overflight's of its airspace so LA was not an option,
This was not only dog in the manger politics but the noise of the four Bristol/Rolls Royce/SNECMA Olympus 520 engines. They were very noisy as ex-military engines usually are,
These engines were from the proposed preproduction run of the TSR2,
SNECMA were engaged because they had a Spade Silencer design that they promised would massively cut the engine noise.
Trials of the spade silencers proved them to be totally ineffective,
With Concorde not allowed to use the airspace of the USA the proposed orders from many American airlines were cancelled,
So with just sixteen Concorde in service and combined with a maximum seating capacity for just 128 all first class passengers instead of the needed 200 seats in two classes it was in trouble whenever the international political and financial situation went south.
And the oil crisis of the 70s did not help.
Surprisingly the tragic Paris aircrash which was no fault of Concorde or its crew had no noticeable effect on passenger demand even though all flying examples were withdrawn while the fuel tanks were armoured and redesigned before being allowed to operate again.
A proposed redesign with bigger engines and a larger mainplane died on the drawing board although in retrospect a stretched longer range Concorde with two classes and 200 plus seats would probably have sold very well to Singapore Airways and Quanta's.
The one saving grace was that the Thomas Delarue printing presses at Loughton got some respite as the 24 hour a day printing of high value £££ notes could be halted.