The more you move up in prices doesn't constitute a greater gain in SQ
More expensive equipment is either geared towards Audiophiles or sound professionals. The difference isn't drastic, but the dependable quality standard is higher.
Rough speaking: More money = More quality you can rely on. Like reference headphones.
As you grow in scale of pricing, the quality improves on a opposite scaling is the X 10^ concept. This means that the more you throw at a headphone, the less quality jump will occur.
A $100 headphone will be anything a person wants and doesn't tell someone else that a $500 headphone will be better by 5x as much. More like, 20% better as above would state.
So $100 headphone would be 100% and $500 headphone would be 120% the quality. 100% + 20% added on.
All this is rough at best, but shows what I mean.
Choose headphones and earphone on the preference of sound at the lowest need since most headphone will sound good. Aim for comfort, build and your personal sound preference according to your musical tastes.
EDIT: And of course, price wise. Don't spend what you can't afford to.
Edit: Can't is with a "t", not a "c"