"we didn't ACTUALLY spend that much on a hammer, we just averaged it out across a bulk purchase! See, we aren't terrible with money."
Framing something as 'the myth of the $600 hammer' is implicitly pointing to external sources (congress, journalists) and messaging that they 'invented a myth' that the military spent $600 on a hammer. They didn't invent anything. They worked with the information that was provided to them by the military.
If you wanted to discuss the same issue, but under a framing that wasn't disingenuous, you could title it something like 'the reality of abysmal and misleading accounting throughout the military and their contractors'.