This is primarily because the Canadian dollar, which was at parity with the US dollar 2 years ago, has been devalued 25% against the US dollar. I know, as I am in Canada once a month on business. Makes for great value in Canada for the US citizen on a lot of other things if you can take advantage of the difference.
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How about the Milsurp Pistols?-- there seem to be quite a number under the $500 USD limit.