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Short Question: How do I calculate market values for different resources in the game?

Long Question:

I am building a game around the concept of resource gathering and manufacturing to gain different resources. Those resources can be traded with other players or with a "game market", meaning auto generated trades that get created on a certain time interval (undecided on the interval yet). Because it would be too complex to create different exchange rates for each pair of resources (there are currently just under 100 types of resources and plans for a few hundred in total), I have come to the conclusion that there needs to be a "game currency" (lets just call it GC for now). Each resource would have its exchange rate to GC and this exchange rate would, on a certain interval, be impacted based on what is going on in the game. How would I calculate this exchange rate or market value of a certain resource every interval? I assume different things would effect it like popularity of trading within previous interval, previous exchange rate, abundance of resource currently, etc etc. But I am not sure how to apply this methodically.

Update: Some of my concerns are around the value of a resource:

  1. Some resources can be mined directly from the environment. Other can only be obtained from manufacturing the mined resources. Other resources may be manufactured for other manufactured resources. How do I create a stable starting point to account for these factors? Obviously manufactured resources would be worth more because they are more time consuming to create.
  2. Should players be forced to observe the market value or place their trade requests at what ever value they desire? If the value is forced, what happens to trades after a market value changes? If the is opened ended, what stops players from gaming the market to boost or fall prices? Should I only calculate the value based on successful trades and consider that open request haven't been filled for a reason?
  3. How do I calculate what will happen in a large multiplayer situation when the game is only in development and I only have myself and a few AI players trading? The market values could be effected differently in different situations and I don't want to be caught in a situation where I have to change game mechanics after a game in live which could potentially upset players who have figured out the predictability of the market and over night, the rules change.
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  • \$\begingroup\$ There are many different ways to determine the exchange rates. Some might be right for your game, some might not. But we don't have enough criteria here in your question to narrow it down yet. Try the most naive thing you can think of first (say, compute each item's share of the overall trades in the previous interval, and adjust its exchange rate by its deviation from the average trade volume), and see if it does what you need it to. If you encounter a problem with your first naive guess, post here and describe the specific problem, and we can help you find solutions to that problem. \$\endgroup\$ – DMGregory May 3 at 17:20
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    \$\begingroup\$ Does this question help you? Designing a trade / market system \$\endgroup\$ – Philipp May 3 at 17:47
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    \$\begingroup\$ In a multiplayer game, something as simple as "when you sell, price for the resource goes down, and when you buy, price for the resource goes up" can be enough. \$\endgroup\$ – Foxwarrior May 3 at 17:53
  • \$\begingroup\$ @DMGregory what more criteria would you need? I can update the question with more details. I am just not sure what to share. \$\endgroup\$ – wesleywmd May 3 at 18:24
  • \$\begingroup\$ @Philipp Not completely. those answers seem to be more focused around buying and selling of single units. Where inventory quantities can vary in my system. New comers might be trading under 100 units at a time and veterans might be trading at 10s of thousands of units at a time. \$\endgroup\$ – wesleywmd May 3 at 18:29
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Common wisdom when it comes to MMO economics is to just let players decide at what prices they are willing to trade resources and equipment between each other. Create a trade platform where sellers can offer items or resources for any price and where buyers can then accept those offers if they find them fair (often called "auction house"). Some games also allow players to post buy-offers on the auction house, but the players in most games rarely make use of this feature.

The law of supply and demand will quickly stabilize the prices at what the items are really worth to the players. This usually works much better than just trying to dictate prices. If you feel that some items are too cheap or too expensive, you as a game designer can try to influence prices indirectly by either changing how easy it is to obtain items (affecting the supply) or by changing how useful these items are to players (affecting the demand).

The question mentions concerns about price fixing and market manipulation. After playing lots and lots of MMOs with free market player economies, I made the experience that this rarely works, because there are just too many players. It is hard to build a cartel when most resources in the game can be obtained and offered by any player in the game. Even creating an artificial shortage by buying up a certain resource rarely works out. It will usually just encourage more players to farm that resource, because they see a chance to profit from the current lack of supply on the market. And if the hoarder then tries to dump their stash back onto the market, people will underbid them with the regular price, so they end up making almost no profit at all.

If you want to find out the current market price, either for your own metrics, as an information for the players or because some game mechanic depends on it, then it is usually best to not look at offers but to look at the trades which actually get executed. Standing offers are not that interesting, because if their price was the actual market price, then someone would take them. The price of the last transaction should give you realtime data, but if you want more stable and reliable data then it can be more useful to look at the median price of the past x trades or of the trades in the last x hours.

However, there might be a chance to manipulate the prices you come up with that way. For example, two players (or two accounts operated by the same player) might manipulate the displayed price by trading items back and forth between each other for greatly inflated or deflated prices until their fake price shows up in your statistic. You might have to take some measures to detect such manipulation patterns and filter out such trades when estimating the real market price. Or don't, and call it "emergent gameplay".


But let's say you really want to avoid a free market economy and want fixed prices instead. There can be good reasons for that, most of all that it makes your design process much easier if you know the price of everything.

In that case it is a good idea to convert the price of everything into play time. The time it takes to acquire that resource. If acquiring a carrot takes 1 minute of playtime and acquiring a pumpkin takes 5 minutes of playtime, then a pumpkin should be 5 times as expensive to buy. If resources can only be bought and not acquired through play time, then you can alternatively try to value them by the play time this resource saves the player. If a potion of dexterity cuts off 5 minutes of the time it takes to grind to level 42, then it is half as valuable as a potion of life which cuts off 10 minutes of time it takes to grind to level 42.

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  • \$\begingroup\$ Since I'm in a similar position as the original poster (except for the multiplayer part), I'd like to go into more detail in the second part of you answer. Since also crafting/manufacturing is a part of his (and my) game, how would you do calculations for crafted/manufactured items? 1) Would you just multiply and sum up the estimated costs of the ingredients? (e.g. a pickaxe is built from 2 wood (cost: 1 round per wood) and 3 iron (cost: 2 rounds per iron): base cost of the pickaxe 2*1 + 3*2 = 8? \$\endgroup\$ – Mischa Magyar Aug 30 at 13:57
  • \$\begingroup\$ 2) Would you also factor in prerequisites? (e.g. you need a workbench (cost 20 rounds) to build the pickaxe: total cost of the pickaxe 8 +20 = 28? \$\endgroup\$ – Mischa Magyar Aug 30 at 13:58
  • \$\begingroup\$ 3) And what if the pickaxe even unlocks some a new biome where you can find some additional resources (e.g. the mine)? Add some more costs to the previous costs? \$\endgroup\$ – Mischa Magyar Aug 30 at 13:59
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    \$\begingroup\$ @MischaMagyar This appears to be a new question you should ask as a new question, but the quick comment-answers would be "yes", "yes, but not the full price if the workbench can do more than just crafting a single pickaxe" and "no". \$\endgroup\$ – Philipp Aug 30 at 14:17

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