The price to income ratio is actually more damning:

https://en.macromicro.me/series/5433/china-housing-price-to-...

Considering the absolute number houses in China were not affordable at any point in recent history.

2010 is often cited as a reference point, most likely because it's when the Chinese stock market started experiencing a slump despite the initial post-2008 recovery, so investments shifted into real estate:

https://www.macrotrends.net/2592/shanghai-composite-index-ch...