Just recently, I was bidding on some 52 Topps cards, which the seller had replied to me that they did in fact ship to Canada, but didn't tell me the fees.
Assuming (bad decision) shipping was likely around $8-$15, I carefully bid on some cards but kept my bids under $15.00 per card. I ended up winning 3 and found out shipping was only $1.45
If I had of known (my fault for not asking) I definitely would have bid higher on quite a few more cards, which I seen, after the fact, they sold for very reasonable prices.
I also think back, when I joined the site, the many cards I seen that I wanted but being uneducated I didn't purchase any only to see those same cards now out of reach for me!