It is a thought also, no doubt, in the minds of the family of the pilot of the F-117A Nighthawk which came down in Budjanovci on Sunday. The dramatic rescue of the pilot was cause for celebration too for Nato chiefs.

But the loss of the Stealth fighter, believed to have cost the US $42m, has put into stark relief the size of the monetary sums involved in modern warfare.

The F-117A Stealth fighter

Political estimates of the cost so far of the air strikes are as much as �2bn, but it's extremely difficult to quantify, says Andrew Brookes, the air analyst of the International Institute for Strategic Studies.

As well as the immediate costs, there is a huge infrastructure which has been maintained for years. Pilots' training and satellite surveillance are all essential to the action, but have been paid for over a long period.

"In sheer bald terms, this costs a lot of money," he says.

Some estimates put the price of the lost Nighthawk fighter as high as $122m.

Which is as almost nothing compared to the B-2 Stealth bomber, each of which is worth a cool $2.1bn.

Price of superpower status

"We're definitely talking big bucks. It's like going to the moon, this is really at the forefront of technology, and that's why Uncle Sam is the only superpower. When we talk about Europe being a defence force, it's not going to happen until we invest that sort of money. I don't think people have thought that through. There's more to a defence capability than having the top brass."

The cost of missiles is also significant. Tomahawk cruise missiles, which have been launched from the US Sixth Fleet, stationed in the Adriatic, cost $500,000 each, according to Federation of American Scientists' figures. That is some reflection of the amount of technology involved in an object with a diameter of just 51cm.

A Serbian boy holds a piece of the downed Stealth fighter

Paveway bombs, the "smart" bombs which have been dropped each night by Nato planes, cost $55,600 each, while the AGM-130 guided air-to-ground comes in at $885,000 each.

Mr Brookes says the cost of the action would "fall where it falls" - in other words, each Nato country involved would pay for its own military activities.

Many of the costs of the Gulf War were recouped by donations from wealthy parties which benefited from the liberation of Kuwait. That will not be repeated after the current conflict.

"People will start asking the question. We're into a long campaign, and bombing night after night isn't going to come cheaply," says Brookes.

Ground troops would push the budget even higher. "People talk about bringing troops across, but they're not going to get there by Stena ferry," he said.

Cutting the cost

The leader of the UK Liberal Democrats, Paddy Ashdown, has alluded to this question becoming an issue. In calling for an international protectorate to be established for Kosovo for as long as it takes to secure stability, he said: "That does mean troops on the ground. Whatever the cost, it will be less than that of a widening war in the Balkans."

Professor Paul Rogers, of Bradford University's department of peace studies, said that barring an unforeseen compromise, the conflict was going to last a long time.

This in turn would raise the question of ongoing cost.

The cost to the UK is only a fraction of the overall sum, he said. And it could be argued that much of it would have arisen regardless of the conflict.

But there were substantial extra costs of fuel and munitions.

"You can spend $10m in just one salvo of cruise missiles," he said.

Climbing up the agenda

The whole question of how much the conflict is costing is a grey area, he said.

Rachel Harford, of the Campaign Against the Arms Trade, said she thought the subject could become a matter of public debate.

"It's difficult to judge, but people are more aware of the issues nowadays, and do ask the question.

"If it's a protracted situation, costs are going to have to come into it."