You need an awful lot of shells to match a 1000lb er.
From what I have read, 10 m is quite inaccurate compared with a cruise or a PGM. True it is 10-30 times more accurate than before but a miss is still a miss against some targets.
And what if it fails to guide? Because it is reliant on ballistics it is probably more likely to misguide short, left or right than long. Could therefore be limited in the gunfire support role.