I bought a lot of stuff from the United States (B&H) over the past two years and had it shipped to Canada. First of all, buy while the Canadian dollar is strong, then expect your credit card company to skim off the top by giving you an exchange rate that is about 3% less favorable than the rate you see shown on the news every night. Now, the duties you will be charged depends on where the items you purchased were manufactured and what they are. I am pretty sure that Japanese camera equipment coming into Canada from the States is not charged duties. Camera related stuff that was originally made in China or Italy will be charged duties. (It's 6.5% for stuff from Italy, and I think less for Chinese items). Finally you will have to pay the full GST and provincial sales tax for your province (unless you are a company with a registered GST number, then you only pay the GST portion). I am not an expert with regards to this stuff, but this information reflects my general experience.
If your item from ebay is used, it may be treated different at the border (charged less perhaps).
By the way, the last order that I had UPS import for me was done so free of charge. I do not have my own broker so they got the shipment through customs for me, and did not charge anything. Maybe its a new policy?