This is a simple way to make going to the market in your RPGs a little more interesting. It creates an inverse relationship between inventory and price of a resource, all in one roll. Quentin Hudspeth developed it into a full RPG supplement for fantasy, modern and science-fiction games. You can buy the fifteen-page PDF here: Playing the Market
Stuff You Need
A bunch of six-sided dice. The larger the amount of dice, the larger the market.
When to Roll
Use this system when the main characters walk into a shady alley to find some black market contraband, ride into an exotic bazaar for magic items, or dock at a space station to refuel. At the moment the characters search for a specific item, use this system to determine how much of that item is available and how much each costs.
How to Play
Roll a pool of d6s. Each die resulting in 1-3 is one unit of a resource available for purchase. Each die resulting in 4-6 is how much one unit costs.
Example: You're looking to buy a sack of beans. You rolled 5 dice and got 1, 4, 3, 6, 2. That means there are three sacks available, because three of the dice rolled within 1-3. Each sack costs 2 bucks, because two dice rolled within 4-6.
In other words, when there is a lot of resource available, it costs less. When there isn't much available, it costs more. There are a lot of little tweaks you can make to this system, like shifting the 1-3/4-6 margin higher or lower depending on the rarity of a resource.
You can see how Quentin Hudspeth developed this mechanic into a full supplement for a variety of genres in his full fifteen-page PDF. Buy it from the link below.
» Playing the Market by Quentin Hudspeth
» Update: Quentin is now offering a deep 25% discount on the PDF until September. Click here for the discount.