There's at least one poster a week asking what camera they should get for their short when they have a budget of $2000. My question is at what budget level do you move up the camera food chain?

I know someone who just finished shooting a $100,000 budget film on a Panasonic HVX200. At what point would you move to the next level of camera? Is there a percentage of your budget you should figure in for the camera (e.g. 10 percent for camera rental...)? Example, if your budget is $200,000 you should use a camera worth $15,000.