Maybe I misunderstood what you were saying... But if they are only charging 1.5 times more for 2.45 more fabric... Isn't that a good thing?
I have found that the wide backings, while more per yard have always been a more cost efficient alternative for me because I am buying much less linear yardage. Wide back I can back a quilt with about 3.5 yards of fabric and no piecing. 44" I usually have to get about 7 yards. (for queen size quilt).