You can get great casual listening headphones for ~$30 these days. They may not be amazing, but they will be adequate for listening to music in just about any setting.
If you're looking for monitoring headphones, or more serious listening headphones, you'd be hard pressed to find anything worth it in that price range.
I made tons of music using $30 philips headphones that I thought were pretty decent, but ultimately, since I've gotten my Sennheiser HD 280s, I can't believe I ever thought that.
That's also my recommendation for this thread. If you search, you might be able to find them for as cheap as $60 or $70, since they usually sell for ~$100 new. They are excellent headphones.