Ebay completed listings have the machine sold for $400 - $550 (including shipping), depending on the accessories included. Grace makes lots of different frames, so don't know if that's a good price or not. As the previous poster mentioned, as you roll the quilt, you will have a smaller & smaller area to quilt, starting with about 7" to maybe 3-4" or so. Having said this there are lots of folks out there who have a domestic machine on a frame & do wonderful work.
Do not buy until you have tried it!