The main thing was heat resistance, and also, the fact that because my hair is dark and my head is big, I need a thicker wig and a wig cap.
Thanks for the links, if I can, I'll try the ebay ones. The reason why I wanted cosworx was because I do the orders through my mom, and if I do ebay, I'd have to go through my aunt.
Not that I don't trust my aunt, but she can be very persistent when it comes to money and things.