The customs fees went to the government of Canada.
The postage cost went to the post office.
The sales tax (more likely than customs) went to the federal and provincial governments)
The customs brokerage/service fee went to the shipper (courier or Canada Post).
None of these were paid to eBay or to the seller, and eBay has no responsibility for refunding them.
Return postage, by eBay and Paypal policy, is the responsibility of the buyer. Contact the seller. She is allowed to waive all or part of this cost.
You can get a refund on duty and sales tax on items being returned by calling Canadian Border Services Agency. The number is on the back of the customs invoice you got when you paid that $112.
