Car is for transportation. Watch is for time-telling. Camera is for picture-taking. Once you get past the basics, you get expensive. Sometimes better quality...sometimes not. Most of the time you get extra features--more comfortable ride, more power for cars for instance. With a camera, you're pretty much assured of excellent image quality throughout the product line because everybody makes excellent cameras today. More money gets you a few features the lower priced model doesn't have but you can get just as good a photograph with either.
Most of us choose the car, watch, camera, whatever based on how it fits into our budgets and lifestyles--it's that simple.