The Ministry of Defence has admitted it has been paying £22 for a light bulb worth 65p.
Defence Secretary Liam Fox described it as "inexcusable" and evidence of a waste of taxpayers' money by the previous Labour government.
The Sun newspaper has published an invoice it was shown by a soldier who works in the stores of a UK base. Defence chiefs are also said to have paid £103 each for screws, believed to be on sale online for £2.60.
The soldier said he could not ignore the "criminal" waste he saw every day.
He told the Sun: "You're talking about a fortune for these bulbs. If I order 100, that's over £2,000. But you can pick them up for 65p each, the exact same ones.
"There must be thousands of light bulbs across the MoD. If people paid attention to simple things like this, they could save a lot of money - and maybe jobs."
The soldier, who the Sun did not name, said specialist contractors sourced items for the military and added their costs on to the price, but large savings could be made by buying in bulk.
Dr Fox told paper: "We are already tackling the procurement problems we inherited head-on. When money is tight and we need to protect the front line, waste is inexcusable.
"This is classic evidence of how Labour wasted taxpayers' money and shows a complete lack of common sense. No wonder the last government left the MoD with a budget deficit of £38bn."
An MoD spokesman said: "Given the current financial situation, we are looking at existing contracts to ensure value for money and taking steps to make efficiency savings."
This is just...I don't even have words.