I'm not denying that you can find the same one at Home Depot for $20. My point is that the military probably will not buy that hammer from Home Depot without a test report stating that it meets certain requirements.
I see all sorts of requirements, such as NO PVC (Polyvinyl Chloride) - a common plastic used to coat lots of things, like hammer handles and wire insulation.
PVC can't be used because if it is in a fire, it releases toxic fumes, which can kill a pilot or a submariner.

Also, we sometimes have to prove (by analysis or testing) that no material used in our product is destroyed by a variety of chemicals - like jet fuel, bunker fuel, sea water or engine oil.

And often, we are must test to prove that the metals used will not corrode when subjected to 14 days of high-temperature salt-fog spray.
We can't perform any of these tests ourselves, the tests must be performed by a qualified third-party testing lab that has *proved* they are qualified to test to a given MIL spec.

Home Depot's hammers may, in fact, meet all the requirements. But will they provide test reports to prove it? I serously doubt it.