If you have any flea markets located in African American communities (or where they shop) you can probably find whatever you need for a reasonable price. I think I paid $50 for 4 ounces (standard pack) of good quality hair.

Keep in mind that it takes a lot of time to learn how to do this. It's really simple but it takes a lot of practice. I have all of the materials but haven't yet had the time to devote to becoming fast enough to do hair adds and such.