Trading mechanics are a powerful way to introduce player interaction into a game. However, freeform trading can massively slow down the game depending on how much players negotiate. If players are allowed to trade anything, they might argue over the proper exchange rate. Even in Sidereal Confluence, where exchange rates are explicitly defined, it is unclear how much the loan of a converter card is worth.
I’ve been thinking about this lately after the first playtest of Dungeon Rancher. Trade in Dungeon Rancher serves the vital role of smoothing over randomness by allowing players to buy from other players the things they could not mine themselves. However, we aim for the game to last 30-45 minutes with six rounds, which means there is little space for lengthy negotiations. We previously let players trade monsters, dice, and rooms, but now we restrict it to dice, the most comparable resource. I don’t know whether this is enough, though.
Most games with trading mechanics don’t restrict what players can trade. In Dune, you can even exchange binding promises about future actions (modern games don’t allow this anymore). In a game like Sidereal Confluence where everybody is trading simultaneously, this isn’t too bad – as long as everybody is engaged, the only effect is to increase the game length. But in a game like Catan where a player can only trade on their turn, this can lead to significant downtime in the wrong playgroup. For this reason, I think freeform trade should seldom be turn-restricted.
But some games have an elegant alternative – fixed prices. In Imperial Settlers, players can build “Open Production” buildings that produce a resource and allow other players to gain that same resource (from the bank) by giving the owner a worker. Setting aside the question of whether this counts as trade, this is quick because there is no negotiation – the owner cannot even refuse the offer, and the rate is always one-for-one.
Root: The Riverfolk Expansion does something similar with its otter faction, which has three different types of goods and services on offer; in this case, however, they may set the price at the end of their turn. The player has more control over their sales but still cannot refuse the trade.
In both Imperial Settlers and Root, trade is indirect; the seller puts out an item at a price on their turn, and the buyer chooses whether to buy it on theirs. This can feel less personal than direct trading between players. A mechanic that I think could strike a middle ground is at-will trading with fixed prices. Say I want to exchange wood for stone; I look up the trade ratio for the two (1:1 for simple games) and offer another player the trade. There is no room for negotiation here – they must accept or reject my offer, avoiding a bartering session. Since the rules endorse the exchange rate, it is less likely that a player will feel ripped off.
I don’t recall seeing this mechanic in any published games. Fixed trade ratios are often used for trading with the supply, not directly with other players. But even when you set the terms of exchange, trades between players are interesting. Trading mechanics are good at compensating for bad luck and make specialization viable while also promoting player interaction. If that is possible without exploding the game length, I think it is worth trying.