heres an excerpt from the ebay guide on shipping from usa to canada using usps....you do not pay any brokerage fees.
FEES: CUSTOMS FEES: 1. TAXES (the most common fee): Canada Customs ONLY assesses taxes (GST or HST) on goods valued at $20 CAD (about $15-17 USD) or more. Taxes are generally about 6-14% (depending on the province destination). A $5 'handling' fee is also added when an item is taxed. When taxes are charged, Customs sticks a taxes-owing form on the box and the box is held by the Post Office as a COD. Recipient pays the tax/handling when the package is retrieved.
- NOTE: Customs cannot check every box, so frequently items valued at more than $20 CAD do get through with no charge -- it's a 'hit-or-miss' situation. Likewise, if taxes are over-charged due to a missing customs form or a seller over-value, recipients can send in to Canada Customs proof-of-payment (eBay invoice and PayPal/money order receipt or cancelled check), along with the customs tax form stuck to the box (make a copy first) to get a refund.
2. DUTY: Thanks to NAFTA there is NO DUTY assessed on goods made in the US or Canada (or Mexico); or on used goods, generally. Most eBay transactions do NOT involve duty. (Yippee!) But duty may be assessed on NEW or high-end used items made ('originating') outside of North America.
Other FEES: There are none! When using USPS/Canada Post the buyer will NEVER get a 'surprise' brokerage fee. Brokers are used by other shipping companies (UPS, FedEx, etc.) to import and deliver items. Brokerage fees can cost as much as the entire item and shipping fees!! But USPS/CanadaPost have agreements with each other to handle each other's mail, so NO BROKERAGE FEES are EVER charged with USPS (or CanadaPost) services! Yippee!