In my experience as a Canadian buyer, UPS/Fedex/Purolator go absolutely bonkers making up bullshit magical 'brokerage fees' and duties when they bring something into Canada from another country. Conversely, I've only ever had to pay duty on a package arriving via Canada Post once, regardless of declared value. It seems like the government can't be bothered to follow up on every single package and collect their fee for it, even if they would be owed duty according to the stated value. When doing any sort of e-commerce I usually reach out to the seller and see if they are willing to ship via USPS/Royal Mail/whatever the government institution is if their default is a courier service, and let them know I'm OK waiting a longer delivery time. UPS state their customs clearance rates here, if your invoice comes with a breakdown of what cost what, hopefully you can figure out what happened.