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"The last card in stock costs 1,5x normal price."

Oh yes, I used it extensively during the beta period. It's the way it's designed. Now I just use the market, sell what I don't care about and buy any I do.

Yes, I used them a lot. Check their inventory in the page, if they have only 1 card left it's 1,5x the value, which is annoying, but with paying attention and being quick it's not a problem.

It's there to make the owner a profit. Don't use it if you're looking for "fair" trades.