Average electricity cost

Alright, with all those talk about XBOX360 eating alot of electricity got me wondering, I'm on my computer alot, about 3-5hours a day, with a 19' inch monitor, around how much would that cost monthly? Just wondering.

>>5 Power suply has no own consumption. But your numbers may be right if we consider 100% usage of all components (e.g. gaming).
>>4 is right if we consider normal usage (e.g. office work or surfing)