Ouch! I got my son a TI84 for $85 on sale at Walmart at the beginning of the year but I don't see any deals now. I would definitely get the model the teacher recommended because they actually use an image of it on the smart board while teaching. When you do get it tell her to watch it like a hawk and ingrave it becuase I have a co-worker whose son got his ripped off. Good Luck!
I just saw this on ebay for sale and it looked like a good deal $67 buy it now from high rated seller
http://www.ebay.com/itm/Texas-Instru...item27c2068718
There are others going for even less.