I suggest being able to pay a certain amount of galleons, to transfer one chocolate frog card from one site (for example EU) to another (for example US). This would be ideal for people who are active on multiple sites at once. The prices could be as follows:
Common - 500 galleons
Rare - 1250 galleons
Legendary - 2500 galleons
This can, of course, be adjusted to what seems best for you!
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