Economy
Bastion, Treasure, and You
Bastion Trade Charter established the port to act as a central, safe point for ships to collect and haul the goods found in the interior out to the markets of the Old World, and as such the economy of the Westlands is primarily commercial and extractive in nature. A thriving artisanal industry exists within the walls, however - from alchemists exploiting the rare reagents found outside the city to the creation of secondary goods whose precursors are easier to find here than anywhere else.
As such, almost anything can be bought or sold in Bastion: canny merchants from all over the world have set up trade consortiums and banks along its streets. Whatever you find in the wild, it can be sold here, and typically for a pretty bit of coin. Most adventurers can live a comfortable lifestyle for a year on the proceeds of a single expedition into the interior - but nearly all trek out from the city more often than that, lured by the mysteries and wonders that await.
Coinage
Bastion secured the right to mint its own coins; it produces copper, silver, gold, and platinum pieces that match the prices in the PHB. Some nations might trade or barter in other denominations, but all prices in the city are set Bastion's coins and they're the easiest way to spend wealth.