From where?
More to the point, sellers set the price of their items and the price for shipping based on their actual costs, the amount of protection (delivery confirmation , insurance, speed of delivery) they want, and what the traffic will bear.
The cost of shipping is totally unrelated to the value of the item. You could mail me a $100 bill for 85 cents LetterPost, for example. Or you could use Priority Post, which gives overnight service, insurance, tracking and signature confirmation, for $44.52.
If your seller is using the Global Shipping Program, you are also being charged an Import Fee upfront. This is a combination of Canadian duty and taxes and a service fee to PitneyBowes, who run the program for eBay.
If the seller did not note that the sweater was made in a NAFTA country, it would be assessed duty.
If the seller did not note that the sweater was used, it would be assessed duty.
Whatever the origin of the sweater, sales taxes of somewhere between 5% and 15% would also be assessed.
And PB adds about $5 for doing the paperwork and getting the sweater to your doorstep.
If the GSP is not involved, the seller may be using an expensive service to cover her butt. From the USA, the best service is USPS First Class International, which moves up to four pounds of product and includes Confirmation of Delivery. However, if the CBSA pulls it for assessment, you would still pay duty and tax plus a $10 fee to Canada Post for delivery. Ask the seller about this before bidding.
