UPS ripoff
My first experience with cross border parcel delivery was similar and I now decline to order anything that has only that option for delivery. If you are not too far from the border you can have the courier hold it for pickup at a convenient northern US town. The holding charge is much less than the exorbitant courier charges. They call it brokerage, but car parts are duty free. If you know someone in the US willing to serve as a parcel drop that is a good option too.
Most of the parts I needed I purchased during a period of two months when I spent weeks at a time in upstate NY. I timed things so that I could ship to the hotel and then carry them back as baggage.
I used to think USPS was a good option, but then I had a $160 underwater camera housing disappear between Houston and Calgary.