I think it depends on the person. For me, I save almost all of my money. If I have a small part time job, I can save my entire paycheck from the school. That would be a different story if I planned to stay and live here. However, since I'm only going to be here for a year or two, I only really spend money on food, and of course basic necessities. I rarely go shopping for clothing or anything else. I think it is fairly easy.

Like Jnus, I think it depends on the person; but I also think it depends on the place. I save over half of my income, but that's probably only possible because I live in a very small city.

Living in a tier one city, I think saving money would be much harder, unless my salary was commensurately much higher, and I doubt that would be the case.

ED:
Thinking further, I think things are quite different for those of us only planning to stay for one or two years (or maybe less... if I have many more days like yesterday the length of my stay will be determined by the traffic on the way to the airport!) versus those here for the longer haul.

For a start, I have a definite savings target to meet post-China plans, and second, in less than a year, my entire worldly possessions (and some of my partner's, going on past experience) will have to go into a backpack that I can carry. That discourages stupid spending better than anything.

as people above have said. Its the way you live.

I'm a spender and buy meaningless items almost each week for example a coal water filter that goes on your tap but I still boil the water.

I still have money left over each month but dont struggle from paycheck to paycheck but could save more if i change the way i spend.

it's different for guys and gals. especially single guys you gotta spend so much money on on dating , searching and other nonsense due to loniliness. also it depends on whether or not you like to cook for yourself. if you are in a city where you can get cheap good food (10rmb meals) then you will save a lot more. 

For me , I've never been a saver, so I buy what I want / need. Yes I spend too much,, hate to even imagine how much recently. I'm paying the bills on my house at home, an apartment in China, buying things I need like pots, hot plates, a scooter and I'm used to just blowing money, my trip here, insurance. bla bla... I don't find China cheap, maybe bus taxi, but clothing etc aren't. I'm spending a lot more than I had planned.

I agree with crimo...single guys in China can get into trouble.
When I go to HK for a few days, I usually brake the bank.
Drinking in expat bars and eating out everyday can add up fast.
I find being single can cost even more than having a high maintenence Chinese gf.

The temptation of nice restaurants, bars and luxary items.

Like any country in the world - if you want to do most things you enjoy you have to spend money.

Walks in the park may lose their appeal after a while.

Lifestyle, although I have a Chinese wife now, I had no problem saving money before. I eat at local restaurants and only go to expat restaurants once a week. I have banked 80 to 90% of my income for 5 years.

Sometimes when people come to China they continue to live the life they had back home. For those of you who are here for culture and tradition, leave the expat bars alone and go and embedd yourself into the culture.

No Offense HappyExpat, I hope your restaurant does well.

For those of you who are here working for a Foreign Company then you probably have no problem in comparison to ESL teachers.