WW2 is the only real example to answer this kind of question. For all the global skirmishes and regular war games and other exercises, since WW2 there really hasn’t been sufficient conflict to prevent manufacturing an ahead of time stockpile of desired weaponry at the prices set by companies in the military industrial complex. Price did come down in WW2 but it can be hard to attribute it specifically to “we used everything we built and wanted more delivered yesterday” when so many other factors are involved. Wartime rationing, production regulations, patriotic decision making affecting prices people charged the government, and the simplicity of the things being manufactured compared to the complexity of modern munitions.

At the end of the day I’ve personally settled on “yes but probably not as much as you might think”.

Multiple sourcing probably played a big role. Lots of companies were making Sherman tanks, for instance. IBM was making rifles along with many other companies.

There is no second source for the F-35.

The U.S. Navy has apparently bought 8,000 Tomahawk missiles overall and we've shot 2193 of them - but I genuinely don't know when Raytheon's volume discounts kick in.

What number would you place on the threat that Iraq posed to the United States? Would it be more or less than $1.1t?