Ah, reminds me of the pre-Grand Stock Exchange days of Runescape when you could sell some shlub a plank of wood for as much money as your uber rare Blue Party Hat if you wanted to...
It started with a small tax but was eventually axed to make way for what I hope EA ends up doing: a centralized purchase system where you could only offer within set parameters - You could offer to sell/buy now at a designated middleground or, if you were feeling spicy, could try your hand at +-15% (give or take). This would either increase or decrease the median price at a moments notice so you'd get a true sense of worth and people couldn't get scammed or really cheat the system with backdoor deals.
Packs could open back up to being tradeable and, one would at least assume, cheaper.