Though I am not an expat but hope what my expat friends' talk with me will give you some reference.
I don't know for how long will you stay in Kunming, for short term or long.
If for short term the need might be around 6,000 - 10,000, depend on life style. 6,000 is more for very simple life style.
Some detailed reference:
3 bed room flat cost 2,000RMb to 5,000Rmb. Depend on the location and condition.
The western Cafes here according to the menu, main dish is around 25 - 65rmb; dessert is around 20rmb; coffee is around 25rmb. a simple Chinese meal in a small restraunt for 2 people can be around 60 rmb. will be 100 - 200 rmb in a very nice restraunt. If you cook for yourself will be cheaper.
Local bus cost 1-2RMB per trip and cab cost 20 - 60 (in city )depend on distance. a electronic scooter cost 2500. for car, you need to ask more reference.
These didn't cover travelling and other expenses but just for basic daily life need.
If you need to stay here for long term then the uper post have more insight about it.