JoAnn's generally charges $20-$30 for classes (at least two sessions per class) and then you buy your project supplies. Is the project included in the class fee? You should ask to see the supply list and then calculate what your true cost would be.
$75 would be pretty expensive if that's just the fee to take the class. You would think that they'd want to keep their price low so that they could turn more people into knitting addicts.