First you have to remember that China itself's population is as large as the entire western world, so things are completely different here. For example, almost nobody in China use credit card for online payment: they use Alipay as an alternative.

1. Perhaps high salary? Non-local employees are rare here.

2. No in tech companies, but yes in small cities and countries. In tech companies and cities like Shanghai, forigners are treated better than locals, seriously.

3. Easier than getting a work in US.

4. Don't send a clock as a gift :)