This season? From what I can see, that record is consistent for Cannon across Preston, Stoke and Leicester (where he was barely used). If we signed him today and played him every week, you would be expecting 8 or 9 goals before the end of the season. That's not factoring in that we'd be creating more chances for him than any of those situations previously and that he's only 22 and has a lot of room for growth.
Last season Frigan managed a goal every 250 minutes and before that he was in an inferior league to Belgium.
I'm not for one second suggesting Frigan is a bad signing. But it's in no way a like for like but half the price. There is considerably more risk that comes with Frigan and Cannon is much more likely to provide an immediate impact.