You probably won't be able to find them any cheaper until they go on sale up here as most brands (Including Union) make retailers sign a contract that prevents them from selling outside the US. So you really only have a few options... You could either just suck it up and pay the Canadian price, Drive down to the US and buy them there (Really only worth it if your close to a border) or you ship them to someone you know down there and then just have them send the bindings to you.
The one thing that really bugs me is the amount that the manufactures mark things up for Canadians. Giving them the benefit of the doubt Canadian dollar isn't quite on par with the US and it may cost a little bit more to ship them up here. But i don't see how that cost could possibly exceed the amount extra we have to pay. With that being said they also they need to ship their products all around the US which isn't a small country... So i don't see why 100km, in my case, would warrant an extra $80(How much more Union Forces cost up here). The dollar has risen up a lot over the past few years but retailers still are using pricing from back when it was really off. I could understand paying around like $20 more but $80 is just ridiculous.
I dunno that's just my rant for the day... Maybe someone can enlighten me on the reasoning for the huge price gap as maybe I'm just missing something.