I’m not sure I understand. Rent in Chinese cities is much more expensive (on a local economy basis) than in the US and Shenzen is a more expensive city.
Shenzhen labor is cheap only compared to US labor but it's already more expensive than several European countries now.
Seriously, manufacturing engineers in Shenzhen have higher wages than Ukraine and even Romania, Bulgaria and Hungary. And yet most electronic prototyping and manufacturing happens in Schengen and not Eastern Europe.
Its labor that’s cheap there not rent.