Modelling something that is near impossible to do "right" but you can give a reasonable model of the economy (eve online is the most successful close match I can see that matches what you're trying to do)
Product A in Region A might be of low value because there is lots of it and getting it to this region is cheap.
Product A in Region B might carry a higher value because it's not so abundant in that region and thus has the cost of being transported to that region.
Now depending on how your game works, if a player can buy a product from a far away region from anywhere in the galaxy then price displayed should be offset by your transportation cost.
Key things to note:
- This is a very simplified starting point.
- Transport costs may vary (think about risk, cost of other commodities like fuel, ships or ship parts).
- Tax ... are you planning on having that in your model?
- Abundance, any resource a user can just go and make / mine for easily
should be worth virtually nothing as it would be simple to flood the
market with such a commodity but with that said if no user is doing
so and the demand rises then the price should rise.
What I find works best when im playing a game is models that shift by themselves.
Each and every transaction that takes place in your market will have a knock on effect not just on the thing that was being traded but to the market as a whole.
Links to products on a market can effectively be traced to virtually every other product on that market ...
Look at the real world, a barrel of oil makes more than 1 product, from fuel, to plastics.
any industry that depends on any of those products would be affected by the price of oil.
but the oil drilling industry needs things like drill bits so will be affected by the price of say diamonds, metals, ect.
But metals need to be proccessed before they can be used and then manufactured in to drills so the metal workers need oil.
And that's a very basic example, when you consider something as complex as your mobile phone it goes completely bonkers.
How I would go about this:
Start with a table that contains all your products and give them an arbitrary value (don't worry if your model is any good this should sort itself out later).
Now set a load of rules and implement a method / function to implement them.
- rule 1: a product on the market increases by X amount for each system
you have to go through to get to the nearest location it can be found
- rule 2: the higher risk to move a product between 2 systems offset
- rule 3: value by X rule 3: offset value by available / demand
Now you can write some sort of GetPriceOf(Product product, Location system) type function that determines based on the output of a chain of rules what the price of the given product might be in the given system.
Then just keep building and building on it until the model feels real.
It'll likely never be perfect, very few companies actually get it right and even when they get it right it's still not real like in the real world.
The other thing you could try is making money as hard to come by as in the real world then based prices on the real world stock market ... could be a bitch to wire up to your game though.