Each Outpost has an abundance of one item (Surplus), and a relative dearth of another (Sought After.)
The Merchant Alliance posts new Trade Routes every Monday at 12:00 AM UTC.
Sought After = SELL!
For "Sought After" items, the Merchant Alliance will pay more than your original purchase price—meaning you will make a profit.
Surplus = DON'T SELL!
For "Surplus" items, the Merchant Alliance will pay less than your original purchase price—meaning you will take a loss.
Where should we buy?
Anywhere! Ye can buy items at a lower cost, if the Outpost has "Surplus"—which means a great profit once you sell.
However, if yer heading for an Outpost where the item is "Sought After," ye can buy that item anywhere it is sold along the way and know you'll make a profit when ye reach yer destination.