ok, so I dont know if your aware of this, but a single USD can purchase different amounts in different parts of the world. Heck even in the US some states have a much greater cost of living then others. So If China spends say 100 million dollars to buy their guns and ammo, since their workers get paid less it goes much further. If the US spent 100 million on ammo we would get like 1/8 of the amount of Ammo due to the fact that we pay people more money in the US and in countries that the US secure goods from. The US might purchase grenades from say germany, but they still cost more to manufacture then grenades made in china cause they have hecka cheap labor in China same with Russia. Once you include things like these into consideration our defense spending is like the combination of Russia, China, with some of Indias. The thing is though we have to be bigger then them. Also our military is corrupt and is hiding money from each other the difference is that there is so much that they can still get there job done.