Supply and Demand Mechanics

Here’s one thought: Make it that there is a maximum number of each item that can be produced (say, set by the number of game pieces). During the game, all of the un-manufactured goods would be placed on a separate supply/demand board, which has different squares to hold different numbers of goods (each for a different price). For example, say that one good is Frozen Concentrated Orange Juice (FCOJ), and a maximum of 20 can be produced. There are 4 price squares, all of which can hold 5 FCOJ tokens. Lets say the first turn I make 3 units of FCOJ. I remove 3 from the first square, which says that FCOJ is worth $15/unit (to represent their current scarcity). Then, on your turn, you make 3 units of FCOJ. Now you take the last 2 out of the first square, and 1 from the second square. The second square now states that FCOJ is worth $12/unit (since it is now more common). However, if I then sell 2 of my FCOJ for $12 each, then on your next turn you can sell yours for $15 each.

Alternatively, if you wanted an unlimited amount of each good to be produced, you could have a board that just tracked the number of goods in circulation, and showed what the price was (though that might be a little more complicated).

Anyway, it’s an approximation, but it’s pretty simple. No math, no calculations, just look at the board. Is that what you’re looking for, or do you want something more realistic?

Simon

I was thinking along similar lines as the previous two posters.

"Supply and demand" (very) generally means the more of something there is (relative to the demand) the less it costs.
In simplest terms then, the very first of something would have a higher value than quantities to come later. This seems to work very well with a "track" on the board.
For example, if you were to have 20 units of Frozen O.J. (from concentrate??) you might have a track of 20 spaces with DECREASING cost. The first might be at $20 and proceed down the list to a cost of $1 per "share", after the market has been flooded (sorry) with O.J.

A variation on this might be to have the cost start high, decrease in value and then return to a higher value as the commodity becomes "more in demand" as the game progresses. So the track might start at $20, go down to$10 and then return to $20 at the 20th slot.
Another way to vary the cost in relation to demand would be to use the simple track method mentioned above and add a multiplier based on (for instance) the "phase" of the game in which you are. Perhaps something like, the cost is what the track says x.75 in the early game, x1 in the mid-game and x2 in the late game. By the time you reach the "end game", where everyone is hustling to get those final few precious commodities the cost might be x3 (or greater). Of course, how you determine the phases is another topic altogether...

Lastly, you need not neccessarily have a seperate track for each item. If you were to group your commodities by "value" you might be able to have 2-3 tracks on your board with counters representing the commodity moving up (or, theoretically, down) with the amount of product in circulation.

You said you had "at least" four commodities. For purpose of my example, lets say you wind up with six.
You might designate three items as "low priced" (on the first scale/track), two as medium priced (second track) and one as high priced (track three).
And each of those different tracks could have different values assigned to them. Perhaps one decreases with supply, one track fluctuates (starts high, declines then goes back up again) and one track increases regardless of supply because of demand (when was the last time the cost of diamonds went down?).

If you combined this with a multiplier for the game phase (even if it is as simple as +.5 multiplier every 5 or 10 turns) you might wind up with a variety of commodity pricing that fluctuates (quasi-realistically) as the game progresses yet is still easy to determine and viualize based on looking at the board.

Check out Container. In this game, players set prices for buying and selling goods amongst themselves. It's an interesting economy and a good game, although it has been accused of being fragile: it only works if all players are reasonably competent.