Currently it shows how much you will get if the item sells, BUT it does not subtract the listing price. This is misleading, easy to think is better to sell on TP than to vendor, in cases where this is not so. Example: List item for 1 G, listing fee is 5 S and if it sells another 10 S is subtracted, for profit of 85 S. But what is shown is 90 S. Suppose vendor would give you 87 S. Would be better (by 2 S) to sell to vendor, even though “Projected Profit” of 90 S sounds better than vendor price of 87 S.
This 85% of listing price is also the number you want to know when crafting an item, for comparing to the costs you spent on the ingredients, to determine whether you can make a profit on the item.