Capot - I was calculating the cost of carrying 20 minutes of additional fuel for every flight. We were doing different sums.
Motorizer - The cost of buying and carrying the extra fuel would be less than the cost of a diversion. I haven't a clue as to what the cost of that would be. But I feel certain that we are talking about hundreds and not thousands.
You can also be certain that your diversion was not done lightly. These things are a right royal pain. And whilst a change of runway doesn't take 20 minutes, ATC are sometimes reluctant to give a lesser, more realistic answer. Probably because they are told to do so. But you have to act with the information you are given and this crew reacted according to the information they were given.
Am I right in summizing if we had been given a clearance ahead of others then those guys may well have found themselves in an equally tight spot?
Possibly but the gap between aircraft is about 2-3 minutes so the effect is minimal. What buggers things up is ATC having to organise a one-off. And then have to deal with everyone else crying "foul" or asking for the same. The only way out is to declare an emergency - and the subsequent paperwork has to match the declared event. And your company may well be asked questions they would prefer not to answer.