Although it may seem like a good idea at first, I can assure you that doing this would almost certainly lead to a massive economy influx based on the fact that there are currently close to 100,000 uncrafted cards in circulation. Just imagine how many diamonds would come into the economy at once as soon as we allow you to sell uncrafted cards (even with a penalty). Cards were never meant to be sellable and will probably never be sellable in that way for this reason.
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