The factor could be as high as 6.

For instance, with your cross income of $10000 per month here, you would feel pretty tight to live because after tax you may only have $6000 to 7000 in hand depending on where you are.

However, with a RMB 10000 per month income in China, you may feel comfortable in most parts of the country. That is a real money!

Now you may see the difference of the meaning of real GDP.