The 8320s are an enormous steal, most IEMs under $100 don't sound that good. If you want that level of sound quality, a similar sound signature, with more comfortable fit and REALLY good noise isolation, Shure SE215 is worth looking at, but they are tough to find for less than $100, usually $90-$100, $150 for the one with apple/android/blackberry. Maybe look for a used pair on the FS forum. I use them for commuting on the train every day, better isolation than my SM3 v2, I think they actually sound very similar to the 8320 but have better defined bass and a less grainy sound.
Overall though you are going to have to work a miracle to find something that sounds as good as the 8320 for under $50, let alone $20. Fischer Audio Eterna has more bass but similar all-around sound quality with more extended treble, it has good but not stellar isolation, and will cost around $60-$70.
