Chinese Defense budget last year was US$151B and in 2018 will be $175B ... so in US$, it will increase by US$24B or 15.9% .. of course in Yuan will just increase 8.1%
For comparison ... US$24B is equivalent to :
* Slightly more than half of total Indian/Japanese/UK defense budget
* About the same as Australian total defense budget
* 2x as Iran defense budget
* 2.5x Singapore/Taiwan/Pakistan defense budget
* 5x Vietnam defense budget
Major part of China's competitiveness and stability in many aspects comes from its ability to produce nearly everything domestically including the subsystems(and price it in yuan), including defence products. While some technologies are not yet at top tier levels (resulting in some imports), still they can produce nearly everything. If I recall they have the most complete industrial supply chain of any nation in the world. Once China masters some key areas like various advanced engine technologies, nominal budget won't really affect them as they won't need to import other than raw material.
Cheap labour is a multiplier for China's budget but I don't believe it is that significant. Defence related products are capital heavy compared to consumer products and other industrial products, the power of investment and technology far outweighs labour costs for high end systems. Though I still think China enjoys a military purchasing power multiplier similar (slightly lower) to the nominal and PPP difference of around 1.5x.
China is probably the only country outside the US that can potentially master all areas of high tech, even Russia has areas it just cannot catch up on due to a lack of a strong civilian sector to offload some of the capital expenditure and R&D. In areas like semi-conductors, China is the only other fully vertically integrated potential competitor to the US (though it would take some years before real competition begins). I think China is perusing Military-Civilian integration to do just that, build a strong defence industry on the backs of the civilian industries, vice-versa. I believe China's industrial policy and focus was fairly successful in building a strong foundation for China's future endeavours.
While Russia is the top dog in nuclear warheads and nuclear weaponry as recently revealed, it is severely lacking in many essential industrial areas. Luckily they will be able to trade oil and minerals for high precision machine tools and semiconductor fab machines with China, good synergy.
All in all China is the only real potential competitor to the US, it's going to be full spectrum, kinda exciting. I foresee great technological flourishing on all sides. Without a good competition, people loose sight of their goals, meaning, and get complacent.