I agree completely with the comments made so far re: USPS v UPS.
I used to mail order thins from he US fairly regularly and I learned the hard way about the infamous UPS "brokerage fee". After that though, when I ensured that the shipper used USPS, I had no trouble and Canada Post only charged the applicable taxes and teh $5 fee as they are supposed to.
But - and it's a big but, Last week I ordered something from ebay and the shipper wanted to ship UPS. I did a bit of an email discussion with him and he assured me that eh could ship via UPS and there woudl be NO fees.
Well, since I had not discussed this prior to winning the auction, and since I like to think you can trust people, I agreed to him shipping via UPS.