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(No seriously, hijack away ... I don't mind. I do it all the time!!
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I find the answer is 'it depends.' You have to watch out for the dollar conversion, sometimes import duty is applicable, GST is always added and it also depends on shipping method (UPS versus postal service), how much the shipping agent charges for customs brokerage, etc.
For most things, I think, after all is said and done and all shipping and import costs are added, Canadian MO vendors offer pretty comparable deals to the likes of the deals you see in the US. (Usually.)