Canada's duty-free limit on shipped imports is $20CDN (about $16USD).
Not all items are dutiable. The most commonly duty-free imports are those manufactured* in a NAFTA signatory like the USA and used goods.
Even those goods** will be charged sales tax. That can be up to 15% of the declared value depending on your province.
The shipper is allowed to charge a service fee for wrangling the goods through the border. Cheapest seems to be the Global Shipping Program at about $5 USD. Canada Post is $9.95. Couriers like UPS run $25 and up.
Complicating things, CBSA and Canada Post informally decided to save taxpayers money, by ignoring low value (below around $100) and small imports, where the cost of assessing and collecting import fees is higher than the fees that could be collected.
BUT
Couriers are required to follow the letter of the law.
So your $13.77 is made up of duty (if any) sales tax (on the declared value) and that service fee.
If you did buy from a seller who is enrolled in the Global Shipping Program, he may know nothing about all this. You should Message him and let him know that you found it annoying. But he is not really guilty of anything and you were warned about it before you agreed to the payment.
If you were charged by Canada Post on your doorstep, $10 of the $13.77 goes to CPO, the item was (probably not dutiable) and the other $3.78 is GST/HST/PST.
At a guess was your purchase valued t $75 CDN (around $50-$55 USD)if you are in Alberta? Or $30CDN (about $22USD) elsewhere in the country?
*Not purchased in the USA, actually made there.
** Including used goods.
