Living costs are more or less similar to Thailand if you want to have relatively nice western-style life.
Salary here is a lot cheaper than in Thailand. For most people around 1/3 or 1/4 of a thai salary. Some jobs pay only 1/10 of a similar job in Thailand.
So going with taxi-motos are cheaper, hiring someone to clean your condo is cheaper, if you need to get something repaired or hand-build it is a lot cheaper.
Food is similar priced. Local food is cheaper, but you will probably buy some that is imported from Thailand and is more expensive.
Internet is a lot more expensive, even though prices have been reduced lately. Three years ago, a 2mb adsl line cost 3,000 USD a month. And no, it is not a joke. Now you can get it for 300 dollars. You can get a slower line that is more than enough for play poker, for around 80 dollars a month, but you will need some kind of backup line. A mobile connection for 20 a month will do.
If you are a newbie to Asia, I agree with the others. Go to Thailand and see what it is all about. It is a lot easier there, and you can buy more or less what you can possibly want. I miss a Big C
Cambodia takes a little more patience, and it is certainly not for everyone. But if you do go through those extra hoops, and see cultural differences as interesting, instead of as an obstacle, then I can highly recommend Cambodia.
People here are more genuine and they are truly happy to see foreigners here. They have been isolated for a generation, and most people will go out of their way to welcome you and show that Cambodia is so much more than Pol Pot and genocide.