Popularity Mechanic for Trading Game

Um, it's a fairly uninspired unoriginal worker placement game with tiles and resources. You know, choose location of your town well, place workers on various tiles and gain resources each turn. You can use these to build with but ultimately you want to hoard the resources so you can trade them.
There are a million board and computer games which work like this and the game itself is mainly something I want to develop so I can use it in lessons, not to sell or for my own enjoyment (although the latter is not precluded by the using it in lessons part).

The main thing I'm looking for is one of the most difficult things to do in a board game. I want to create a mechanic for a market.
On a computer it is very easy - well, assuming you can program - outside a computer I'm not sure how this could work.

Example of what I am talking about: Player A has a lot of lumber (just a generic resource - "settlers of what?! - no, I've never heard of that game...) player B has a lot of stone. Without any mechanic the two players could trade lumber for stone 1:1. Unfortunately B controls all 3 sites where stone is available and so the value of stone increases dramatically.
Then there is a situation where a "craze" develops for a certain resource, for the next however many turns that resource is worth 5x what it is normally worth. The more common an item is (the more players own it) and the more it is traded the less it is worth but the more it is used, the more it is worth. I also want to build in an "honour" or something mechanic whereby players get a higher rating by not being utter bastards and so their goods are worth more because it came from them.

So here are my ideas for how it would work

1) the boring way:
It is all calculated, there are thousands of Byzantine rules which makes this game into a highly mathematical affair. "calculate present value for lumber, add 4 as value for player's honour/reputation, multiply by 1.5 for market increment..." - If you're telling me that NO, that is the FUN way and the more calculations the more fun it is then you might be what is commonly termed a "nerd". The straight up number crunching wouldn't work with the craze thing, so I'd have to make it so the crazes happen at regular intervals and you could roll for the next craze resource or (yuk!) they could follow in sequence.
-I don't like this method for two reasons: 1, it is boring and restrictive and 2, it is my aim to use this game as a fun way to introduce business, marketing and accounting students to a lot of technical English in a more fun way. If I have to explain a complicated set of rules for 3 lessons before we can play the game it kind of defeats the purpose.

2) market cards:
So you'd draw cards which have an influence on the market, you can keep some and play some but you have to play one per turn. The cards may last a different number of turns depending on the individual cards and the players use these to virtually "build" the market in the middle of the game. The problem is that I'd need to make thousands of cards and the tcg mechanic might arise where is is all about getting control of "super cards" instead of playing what you have strategically - that is to say unless I carefully balance the card set which is more work. Anyway, the thing with the card system, which I like a lot, is that it gets too big and steals the focus from worker placement, territory control and resource monopolisation aspects of the game. It also requires a lot of players of roughly the same level of skill to make it interesting otherwise one will just manipulate the market to hell and win the game even though they have barely bothered with the other aspects of the game. I also want the principle of "outside forces" to feature somewhere in the market.

3) Dice, RANDOMIZZZZEEE!
I'm a deeply random person, I like random stuff. This more than satisfies my craving for "outside forces" but almost totally eliminates players' abilities to influence the market - I'm not going to point out what is wrong with this method since there are hordes of seething anti-random war-mongers who'd do this for me if I gave them the slightest hint that I was leaning this way. Seriously, even I would get tired of rolling for this and then rolling for the whatever else multiplier, rolling for consumption rates, rolling for the resource which is the object of the craze, rolling for how much it is worth, rolling for how long the craze lasts, rolling for how much player honour/reputation effects prices during the craze...

4) "choose your own (economic) adventure!"
This is the best compromise I can find between the various methods.
The cards would be replaced by a story with decisions and consequences, similarly, the number-crunching and fussy rules could exist, but would not always have to be implemented, sometimes the "safe" choice might have unexpected consequences. Dice could also feature, but the market needn't be built around totally random dice rolls.
The problem is of course writing the story! I mean I don't know how markets and economies work or I'd be making money instead of playing with ideas for millions of games I never get round to completing to the point where they can be published. I'm already writing short stories and novels about things perhaps slightly more interesting than the market...

Do you have any ideas, opinions on which method would work best, suggestions on new methods or things I could implement, suggestions for combinations of elements, etc?

Also, this is a general idea in development phase so if anyone comes up with a good idea they want to make money off, perhaps don't post it here. I´m totally ok with people splicing any good solutions which I choose to use or don't into their games.
Come on, let's see what we come up with (wish we could all meet in a dimly lit cafe over coffee to discuss this)