Just buy a $40 GVP one from Sally's.
I had a couple CHI's. They used to be totally worth it because most sucked and came nowhere close to straightening my curly hair or keeping it that way, but now most are pretty good. Technology just advanced I guess.
I've had my pretty cheap GVP one for 3 or 4 years now, and it still works perfectly - and my hair is crazy curly naturally. Plus I like that I can easily adjust the temperature when it's less humid and my hair requires less beating into submission.