A better pair of headphones will:
- have less distortion
- amplify evenly over a broad range of pitch and volume
- be more durable
- fit and stay in your ears better
- block out external noise
- be more stylish
- have special features, like water and shock resistance
There is a also a good deal of marketing and audiophile BS involved, and some of these differences are only something a trained ear would notice. The difference between $5 and $30 headphones are pretty clear, after that, things start to get a little dubious.
Note: Just to be clear, by "dubious", I don't mean headphones stop getting better at $30. What I mean is it becomes less clear whether you are paying better features or marketing hype.
