I own a fair collection of earphones and headphones and I am NOT a fan of the *average-sounding* Beats headphones. The ones in my ears currently are the Sennheisers MX365. For iPod/MP3 usage, they work well enough. They only cost about £15 here, which is significantly less than your $50 budget. If it's just MP3 playback you want, then there's a good amount of Sennheisers/Skull-Candy headphones that work very well for your purpose. As someone above mentioned, in-ear is often better, particularly for general purpose.
I have bought Treblab X5 and I am pretty satisfied with them. These earbuds really put out a great sound. When using in a phone conversation I can hear my friends very well..The noise cancellation is very thorough. I love the compact little case too. After having tried several brands of earbuds, I would recommend these. Excellent for the value.