Oh my that sounds pretty horrible indeed! Poor sweet baby, just goes to show how lucky she is to have you!
FYI, last time I got teeth cleaned it was right around $100, and her teeth were REALLY yellow and full of tartar. It was on a Welsh Corgi and she was only 9 months old, but she just did not have good saliva production so she got tartar really quickly. I think that price was very reasonable for how nice and white her teeth were afterwards!