Oh great! Another non-sensical proposal. What cost? How do you establish the cost? You can use in game vendors, gather your own mats, you can get some as rewards from quests/dungeons, you can send retainers away while you make gil doing something else, use beast tribe currencies, gems or use the MB. The price of materials and items can also have wild variations on the MB. And time cost? lol Oh and some items are already crafted and some are sold by vendors or dropped by dungeons!
Gathering some mats can be way more trouble than crafting which is just assembling. And how is 200% of whatever the "cost" is not overcharging? If I go treasure hunting for a few hours and bring back 3 rare mats, why would I even sell the mats if I can just assemble them into a jacket and sell them for double the price than I would if I sold the mats separately? After all, the real work was gathering the mats. And what is my cost? What if people want the shoes more than the jackets? It is still the same cost to me, yet the demand varies a lot.
Market price is whatever people are ready to pay for the items. Why wouldn't I be able to sell a mat for 1.5mil if someone is ready to buy it at that price? Gather your own mats if you are not happy with the price. If an item is not worth crafting to sell, then don't craft it, sell the mats if you have them and craft something else. If the mats don't sell, prices will go down.I take all that into consideration when I decide to sell mats vs crafted items. It sounds like you just want cheap mats to craft into items that you can sell at high prices.
I don't have any trouble selling on the MB. I take into account the sales history, age and nature of the item and make a decision as to pricing. Very often I will not price my items the lowest and I ignore the undercutting wars. I know my items will sell, it comes down to whether I want a quick sale or if I am willing to wait.