As you seem to know, items over $20 in value are subject to duty and taxes. What the charges will be depends what the item is and where it is made. Items made in a NAFTA country (all that 'free trade' stuff) should have no duty, - but tax, sure. Taxes you pay according to your province, just like buying locally. Duties are not huge, usually around 9-13%, but could be as low as 5% or as high as 18%.
Canada Post charges $8.50 to process the loot for Customs Canada, - as you know. But couriers charge a lot more for the service, and UPS is especially bad, so avoid couriers if you are frugal-minded.
So it's a fairly simple formula: start with the item price, plus the (possible) duty, tax on the item price, $8.50 processing, tax on that too. Add it up and that's what you pay before you can get your hands on it.
That is, if your items get assessed. When they come by the post they often do not. Couriers, however, always charge. But quite often mailed items just show up at your door. Don't count on it, though, because you never know. And always be prepared and willing to pay if necessary.
Here is a link about importing by mail if you would like to poke around in it:
http://www.cbsa-asfc.gc.ca/import/postal-postale/duty-droits-eng.html
Happy shopping. 🙂
