Neither is .223, yet people still buy those. There was a thread a while ago about people wanting a 7.62x51 version of a Cz858 and there seemed to be enough interest in it, and that is certainly not as a cheap as 7.62x39. I would be willing to pay as much or a little more perhaps for 5.45 to get another cz-858 in that chambering. I personally think the price would be comparable. I have looked at some 5.45x39 on some American sites and it seems to go for 180 per 1080 rounds. So in Canada, youd pay a bit more but I still think it would be worth it. I'm positive that if such a rifle was made that it would do well in Canada, provided we had an importer bring in surplus ammo.