>So instead of an exchange rate conversion, you should be doing a purchasing-power conversion. For these three countries, that means multiplying by 3x or 4x.
Where did you get those numbers from? According to the OECD the renminbi PPP rate is 4.198 whereas the the current exchange rate is 7. That's 1.67x not 3x.
https://data.oecd.org/conversion/purchasing-power-parities-p...