I don't think there is any way to make overseas trades economical so only the opportunity to get cards not available in N.A. would make it worthwhile. I will add two recommendations to all those looking to economize:
1. Go to your post office website (Canada Post or USPS) and print off, bookmark or whatever their rates for envelope mail as well as small packages. Many times it costs the same to ship 50 cards as it does 100 cards; 250 cards or 400 cards.
2. Buy a small digital scale (I think I got mine at Staples for $20). They are superbly accurate so you can actually maximize the weight to the upper limit of the weight category you find yourself in. So if you are over 200 grams but allowed to 300 grams before the next jump in postage, increase your trade to maximize the weight even if it means browsing the other member's traders for cards not on your want list. I have done this several times to make larger trades even more economical. Also helps in reducing the traders piles in my card area.
And for Canadians, register as a small business with Canada Post. You can then use their site to do all your own postage for packages and get a discount as a small business that equates to about half the tax charge. As well, come October you get to ship a package every Tuesday for free.
None of us have so much money that we can not look to save where we can. By looking into things and testing the system, I have found ways to do so including knowing which post offices to use and which to avoid.
Bruno
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Check my Profile page to see my 2023 Goals and my Lists of sets near completion (5 cards or less) or sets getting close (less than 100 cards missing and 75% complete).
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