If you are buying from a US or UK seller who used the Global Shipping Program, you will be charged import fees which cover Canadian duty and sales taxes and a small (~$5US) service fee to Pitney Bowes, who operate this Seller Protection program for eBay.
If the seller has not opted to use the program, you are responsible for duty and sales taxes and the carrier will not turn over the shipment until these are paid. The carrier will also charge you a service fee (under various names). The lowest fee is from Canada Post at $9.95. Couriers are much higher.
If you refuse to pay the import fees, the item is considered Undeliverable. The seller is not required to refund on Undeliverable purchases.
You can tell a courier that you will perform the customs brokerage yourself and save the service fee. Compare how much your time costs you with the service fee. You will still be paying the import fees. BC minimum wage is 23c a minute.
To further confuse things, until recently the duty-free allowance was only $20 and CBSA officers decided that it was a burden on the taxpayer to have well-paid officials assessing and collecting piddly amount of duty and sales taxes.
So they were ignoring small and low value packages.
The increase in our duty-free allowance to $150 has only been inforce since July, so we don't have any practical experience about whether the informal policy still applies when the declared value is over $140 but under maybe $500. Personally, I suspect not and we will start hearing complaints as self-isolating buyers start Christmas shopping.
