* wedding gift
* "business" expense that you did out of your pocket (take your co-workers to lunch, buying gift for your clients)
* gifts (giving red envelopes during Chinese New Year, friend / elder birthday)
* rent
* personal saving
* family support (especially supporting your parents)
* medical expense (for a lot of people they have to pay before they can see a doctor)
Here is an article http://business.sohu.com/20131210/n391561808.shtml. Many people can only afford a tiny room today in the city and this depressing phenomenon is coined "蝸居" (snail house, about 10 square feet, and sometimes less, or sharing that tiny space with two or more people), and has been televised and documented multiple times (e.g. a TV drama called 蝸居 was made a couple years ago).
If you are a blue collar working at a city far away from your hometown, you have to go back to your hometown at least once a year (during new year break), and usually it is expected that you have to get a lot of gifts from the city for your family and your neighbors (to thank your neighbors for helping your family / keeping an eye on your family in your absence).
You can almost say the Chinese culture is all about showing gratitude with gifts, this is why e-commerce is such a big deal in China (also why foreign brands like Apple can make so much money in China ;-))
I am asking about these two specifically because they make the biggest difference between the "western" culture and the Chinese culture. The other items on your list also appear in the lives of the citizens of many European/European based countries.
Costs in the large Chinese cities (which includes Beijing, Shanghai and Shenzhen) has been steadily increasing over the past couple decades. It can still be seen as cheaper to live depending on what you compare it to (e.g. SF) but to give a point of reference, Shenzhen is on par with Berlin in terms of cost of living (http://www.expatistan.com/cost-of-living/comparison/shenzhen...). Shanghai is actually more expensive than Berlin too, Beijing is slightly cheaper.
I couldn't have comfortably lived in Shanghai back in 2005 with 3,000 RMB, and I'm extremely frugal (I don't drink, don't smoke, don't go out and my main hobbies include working out and reading).
But I could assume that the welding is done in Shenzhen (maybe GP chips in where he sources welding at 3$/h?).
http://www.numbeo.com/cost-of-living/city_result.jsp?country...
That hourly rate wouldn't even covering rent of an 1-bedroom apt outside of centre.