Comparing levels of military spending among countries is misleading.
And obvious example is trying to compare China's spending with the US. Superficially it would appear that China's military is only about a third of American if you go by spending. But the truth is that China pays it's military personnel one ninth as much. When you consider that, if they spent one third as much as the US on personnel they have 3 times as many personnel alone. While that ratio isn't necessarily across the board you can see how they spend less on manufacturing weapons and systems and still get more bang for the buck. So, what $146 billion bought the Chinese in 2016 is equivalent to about $1.3 trillion for us. That's over double US defense spending for 2016.
http://www.cnn.com/2017/03/04/asia/china-npc-military-budget/index.html
https://www.defense.gov/News/Special-Reports/FY16-Budget