are you sure that isn't for the finishing machine quilting? I used to send my tops and backs out to have quilted, and it cost me 35 for a full size and she supplied the batting (poly, of course). If you wanted to send your own batting you could and she also had other that you could purchase from her. I had a queen done and it was only $55.
Maybe what you saw was the quilting, not the construction price????
Barb