To have Canada Post clear a package from abroad, if gets routed through Canada Customs, they now charge an $8 brokerage fee. it used to $5. To that they will add on GST and PST if your province has it. International duties are uncommon now, so rarely will an imported item have a import duty on it. Seems like the decision point on going through Customs is a contents value of about $150. Sometimes below about $150 they may skip Customs.
The fees that the big couriers ( UPS is the worst offender ) charge for brokerage ( clearing your package through Canadian Customs - a matter of submitting the RevCan/ CC form filled out correctly and accompanied by the shipper's waybill and a commercial invoice from the seller ) is extortion. When I lived in a big Canadian city that had a Canada Customs office, I used to clear my UPS international packages myself and avoid the extortion. That used to get the UPS guys so choked, but it's your decision who will clear your shipment through customs, not theirs. You don't have to be a customs broker to do it, anyone with half a brain and a pen can do it. You do have to collect the shipment waybill & commercial invoice from the courier's office and go to the RevCan/CC office and submit the brokerage documents, wait 15 - 30 minutes for them to be processed, then take the "Cleared Customs" receipt back to your courier and get your package. In Vancouver those offices were right beside each other, out by the airport. Most people don't have the time or freedom to do that, so they've got you by the short and curlies !!
Now that I've moved to a small town, no more international shipments by UPS. If a US seller won't ship USPS, then I use Ship-it-to ( http://www.shipito.com/
), a California service that accepts UPS or courier shipments and then forwards them on to you by USPS.