$30 won't get you great headphones but if you wan't in ear ones you could probably pick these up for not much more than that:
Sennheiser CX 300
http://reviews.cnet.com/headphones/sennh...27753.html
Pros:
-Great sound, both bass and clarity, you can't even compare them to your run of the mill headphones.
-Very well insulated, you can hardly hear a thing happening around you which means you don't need to destroy your hearing and have your music on a million volume to hear it properly.
-Comfortable once you get used to them.
Cons:
-You can't hear people yelling at you
If you want ear-muff style ones spend the extra cash and get these:
Sennheiser HD212 Pro
http://reviews.cnet.com/headphones-heads...69535.html
Pros:
-Very comfortable
-Well built and durable
-Superb sound
-Look sweet around your neck
Cons:
-Fairly expensive but not overly expensive, I consider them to be good value by comparison to others and for what you get.
-A bit difficult to carry around with you all day but they are comfortable around your neck.
-Very long lead for some reason...
Either way I would go Sennheiser, they are good quality for the price,
don't go skullcandy. I had skullcandy's in the past and I thought they were great at the time but they were flimsy and broke and now after having the Sennheiser's to compare to they were pretty poor.
For the record I have both the HD 212 pro's and the CX-300's so I'm recommending them from experience.
Also, for anyone asking why spend lots of money on headphones? If you actually tried them you would find they make music much more enjoyable and they can save a lot of hearing damage over the long run for those who really like to "feel" their music.