I sell an item in the market wards for 10,000,000. It costs me 100k @ 10% tax rate. Yes, it is high, but that is the point. Ultimately the fee would have to be adjusted to a level where it is higher than a market fee for selling the same item in a bazaar. The pay off is that you get the potential of making a lot more money than you can in a bazaar sale, and you can sell it to people across the world. Keeping the cost high limits the items being sold to high-value items. You won't sell a 100g shard with a listing price of 100k. Maybe at this exact moment 100k might be to high, but I think its as good a guess as any come PS3 release.