You could try opening a Dispute as Item Not As Described. The difference being that a cheaper shipping method was used.
EBay may or may not go with that. And eBay may or may not require you to return the item (with Confirmation of Delivery to China, which costs over $40) before processing the refund.
The seller may have done you a favour. Postal purchases usually go through Customs without being assessed for duty and Sales Tax.
Couriers are legally required to collect these.
So if your item sold for over $16USD ($20CDN) the seller saved you the duty, the Sales Tax, and a $25 or more customs brokerage fee from FedEx.
He may not have planned to save you money. Unintended consequences.