They estimate 175k guns in the country, 32K have been turned in. As of the end of this year, the amnesty expires and you're just a flat out criminal who's address they technically have. A couple weeks ago they announced it will be a permanent amnesty.
It turns out offering someone pennies on the dollar for something doesn't yield a lot of response.
In the case of the SKS in Canada, there are at least a couple hundred thousand of them in the country, and they aren't registered. So aside from knowing who has firearms licenses, and that any license holder may own one, they have no way of knowing where they actually are. They go for about 200 bucks "new". It's kind of hard to imagine it being worthwhile for someone to turn one in for 50 bucks when the RCMP has no idea where any of them are.