Hey. I really don't think there is a decent pair of earphones under 30$ unless you look at SkullCandy, but those don't exactly work since they break a bunch. Even though they're more than 30$, you should check out the iP-HS2's by Maximo, they are very cheap for everything you get and the sound quality is amazing. Look up some reviews. Almost all of them say they are on par with the sub 100$ earphones.
iP-HS2