I agree with most everything said here, but the quilter should have informed her of the price adjustment before doing the work. Bindings are not difficult to do or to learn, and your wife might have decided to do that part herself given the choice.
Quilting can be an expensive hobby, but it is also the most gratifying undertaking i've ever done. Please don't get in the way of her developing passion by nit picking about the cost. It's cheaper than marriage counseling.