From my blog.
About making money in games:
(This is not limited to RPGs though I may use that as a topic, and no I don't mean making REAL money off of it)
It seems hard to balance doesn't it? Maybe it's too easy to make money. Maybe you're constantly looking for money. Maybe it's only like that until the end, when you have too much money left over. There may be multiple currencies. You may want to do away with currency and have a barter system, or use "currency" for other things instead of purchasing equipment.
First off, you should consider what to call your currency. Gold is easy to recognize, but maybe you want to vary it up a bit. As long as it's easy to tell that it's money, you can call it (or have it) as you want. Fallout has you trading bottle caps (I didn't know this at first actually), some games have you collecting various items to trade (Feather x 10, Ruby x 10). It depends on the culture you have going on in your game. Do they use salt to trade? Gold coins? Dollars? Do they call them a certain name? (Lucre for example)?
How easy is it to obtain? Pretty easy and you can generally afford what you want to get when you get there, or you're just scraping to get by, selling even your own equipment because you have nothing else? This, along with the name of the currency, can be very dependent on the setting you wish to create. Something like Fallout or another game where the character is struggling to survive should have currency hard to get. Other games can be easier to obtain it, as they may be a higher status. FF8 had a salary, and some games earn you money from renting out houses. Although this can lead to...
The issue of having too much money at the end game. Some games are more problematic than others at this though. You get some games where you're like "I bought everything, I have a bunch of money left over and I keep getting more, now what?". Some have high value end game equipment that is so expensive you feel you'd have to grind for years to get it. It can be hard as you may not really have much else after the player buys everything they wanted to. But it can be something to think about. Maybe the player can spend their gold on something like buying things for a players house, paying rent for more item storage (so the player can carry 200 items instead of 100), or have a rare and expensive items be available that can be bought.
It is possible to manage currency in different ways. Maybe instead of buying equipment, you use points to upgrade your skills and just find the items or have enemies drop them. Maybe you trade in currencies/items for new ones. Maybe you get monster drops and sell them. Maybe you only have a salary and have to use that. Some people like the monster drop because they feel getting gold directly from enemies makes little sense. I personally find it easier to see the gold right there so I don't have to estimate how much I'll get, but it's nice getting a big amount when you sell a lot of items. I also like the drop system when I can get usable and even good equipment from an enemy. You could loot the entire equipment set from an enemy in Oblivion, I liked that. Although the downside was that it made animals/monsters much less desirable to fight.
The amount of money you make on a quest or treasure chest should be proportional to the amount of work it took to get there/achieve it, and where you are in the game. A very simple fetch quest on Level 1 shouldn't make you rich, nor should a difficult quest on Level 30 give you 5 gold and send you on your way. Same goes for treasure chests. If you make the player go out of their way and have to fight quite a bit of fairly hard monsters to get to it, you should reward the player and not give them a cheap potion for their efforts.
The placement of places to buy can also have an effect on your game world. You might have a shady dealer on the road. Maybe a merchant on the road will charge less because you don't have the vendor markup. Maybe there's a used merchandise with reduced prices (but slightly lower quality) goods. Maybe you have a goblin merchant in the lower depths of your dungeon in case you need more potions there. Maybe you can send your dog to go to town and buy stuff for you so you don't have to leave a dungeon. You don't need to always have a town -> cave -> town -> dungeon -> town simply because you need a place for the players to rest and trade. Some games only have one town that you can town portal to, or have full restore spots and treasures around so you don't really need towns.
It is possible to also have item values change depending on the location and needs of the area. Fable plays around with this idea, so you can give some merchants who are low on goods and sell stuff you bought in an area where it was plentiful and make a profit that way. Certain games (tends to be more of the open ended western RPGs) have stats that influence how much you buy/sell for. Bartering or Persuasion or whatever they decide to call the skill. Basically if the merchant likes you more, they'll charge you less. Maybe you can also give free gifts for a frequent shopper, or one that made a big purchase. "You bought 10,000 Gold worth of items from the store, have a free Armor Polisher to go with it!". Some towns might charge a higher tax on all goods, or maybe the events going on in the game can effect the economy. If there are goblins in the mines, it might raise up prices for equipment that relies on that ore until you clear out the mines. Then miners can get to work and lower the prices on the equipment. FF5 had an interesting, though short example:
-There was a fire town you arrived in. They had equipment you wouldn't be able to get until later, at a lower price. But when you buy one, you are arrested.
-After that, due to the plot, you find out the power of fire is weakening. You defeat the boss who is controlling the queen, but the fire crystal breaks.
- Without the power of fire, they can't use it to make the same equipment for cheap, so the price goes up and you have inferior weapons to buy.
Other story related or area related causes can change or set prices in the world. Wine made in a certain town will be more expensive elsewhere, but cheaper in the town its from.
It's just something to think about when working on your game. Your game doesn't always need a deep economy, or things like that, but it's always good to at least think about your gameplay ideas and see if you find something that fits well.
Maybe this could go in game theory and design instead but it's almost 4 AM so I just randomly posted it here.