My aunt introduced this Taiwanese Online store to me called PChome US that sells among many things, cheap yet trendy clothes. It's similar to the very much loved YesStyle and Mart of China, but much cheaper. A downside is that it is in Taiwanese/Mandarin, but don't worry, Google Translate translates the entire website into English (I think, if you use Google Chrome).
Shipping to the US is only $10, so I picked up a couple things and everything was less than $10! By the way, just be careful with the quality since it IS so cheap. I was able to determine the quality by looking closely at the pictures of the material they provide.