It's 500W for only $40. Is the cheap stuff a ripoff? I don't understand how some is so expensive. What makes the others differ? Just wattage or something else?
You have to realize that the power supply has to have enough power to charge everything in your system. The video card uses the most power. That is why a lot of people go by what video card they have and use their judgement on the rest of the components. The video card itself doesn't necessarily use up the entire 450watts (depending on your config). Most powerhouse systems run at 550watts to 600watts with some pushing 650watts. That is crazy. Again, it depends on what part you are using. A simple way to determine this is by doing this: look at every single part and find the wattage rating. Add them all up and add another 25% to it to give you some headroom. That's a theoritical total.
*Fact: Microsoft Window's Blue Screen of Death vs Computerforums.org's White Screen of Death. Which is worse?