I think (not 100% sure) that duty should have a standard rate...
but brokerage fee could be whatever amount they feel like to charge, I had a very bad experience with UP?, the brokerage fee was about 50% of the item's value, since then I've been trying to use USPS for shipping from US, they charge a reasonable brokerage fee
not sure how is UP? brokerage fee shipping from Asia...
Why don't you ask the seller declare lower value? You don't need to pay any taxes at all as long as the parcel is under $50-60 (not really sure). But you can check it in Canadian Custom website.
If You're Going To Beat Me, You'll Have To Bleed To Do It!
Buying local is good but not too much choices and most of the model are outdated. So that's why I prefer to buy from ebay etc. Canada is not a shopping paradise like HK anyway.