Dr. Diff is correct, UPS is absolutely brutal to us north of the 49th. I got a real good taste of it when UPS brokered a clutch when they were told not to because it was being brokered by an independent broker. The UPS bill was 500 something, the independent broker bill was about 140.00 for the exact same service. UPS wanted the money and then offered to match the independent broker bill, which I declined.
USPS to Canada Post is the best way for smaller stuff to Canada in terms of cost.
For bigger, heavier stuff, the other way that I used with Dr.Diff, is to have it shipped to Montana Mailbox by whatever means, and let Montana Mailbox(aka DYK Post) bring it across the border and broker it. A lot of places offer free shipping or reasonable shipping within the US, using DYK works out quite a bit cheaper
than UPS, but it takes them 1-2 weeks to process it.
For work stuff I use a commercial FEDEX account with an independent broker, but some of the packages look like they were kicked all the way here.