When you learn the associated Boost technology, which is to the immediate right of the triple of improved Goods technologies, you will get an additional 3 screens. For each of the three tiers, there's a 20,100, and 500 unit option.
Note that you have to PRODUCE your boosted goods, you can't get them from the Wholesaler, and further that the Wholesaler is only interested in the non-boosted goods within the same tier.
It's also worth mentioning that the WORST trade that other players can offer is 4:1, which ends up being 6:1 by the time you add the fee for trading with an undiscovered player. At 5:1 the wholesaler can never match a 1 star trade, nor any trade with a discovered neighbor or a fellow traveler.
Sooner, rather than later, you'll max out the Coins and Supplies in your Main Hall, so don't hesitate to trade away your unboosted goods. They're actually easier to replace than your boosted goods, because of the way the Wholesaler is configured.