Comment by SpicyLemonZest

Economists account for the divergence you're describing with a concept known as "purchasing power parity", which does indeed result in a 2x adjustment in Chinese wealth. The intuition is that market exchange rates combine a number of things beyond the purchasing power of comparable goods. For example, if you have a 30 year horizon it makes perfect sense to trade 1 car worth of RMB for 0.5 cars worth of GBP: with the GBP, you can buy a government bond at 5.29% instead of 2.26%, and even with no reinvestment you end up with 1.794 cars worth of GBP vs. 1.678 cars worth of RMB.