This is one of the good things about the Global Shipping Program (There aren't many).
Commercial carriers are required to assess and charge applicable duty and sales taxes. They then add a "customs brokerage charge" for their trouble.
UPS is particularly hated for this. FedEx is sometimes sneakier, delivering then invoicing later for the duty, tax and fee.
Most couriers charge $20 -$25 or more.
Canada Post charges $10, but CBSA overlooks most parcels that are valued under $100 or are not bulky. Most Canadian buyers have never paid these charges because of this policy.
The GSP (Pitney Bowes) charges the lowest service/customs brokerage fee - around $5- but like other couriers, must charge the duty and sales tax. This happens before the payment is completed and the purchase shipped, but it shocks buyers who have only had shipments through Canada Post before.
There are older threads, years and thousands of posts long, about UPS in particular. Search Board for UPS. Gouge and ripoff are also commonly used terms.