For a lot of Western cultures, money was worth the value of the precious metals used to make it... this doesn't quite work for the current value calculations (https://dwarffortresswiki.org/index.php/DF2014:Item_value) of Dwarf Fortress, by the current value calculations, the item identity alone multiples the value of the base material, and then quality multiplies it further, so the raw materials aren't worth much. I think this is an entire issue in and of itself that needs to be vastly reworked (I could write a wall of text and all the conceptual problems this approach causes). Assuming it was fixed, then coins would make sense as a way of dividing up metal into smaller portions to be able to use it to buy goods. Historically, money also worked as a way to standardize the weight/purity of the metal, so that people don't have to constantly weigh it or check that the metals haven't been debased/alloyed with cheaper metals.
The idea that money was worth the value of the precious metals used to make it is a common historical myth, but it is a total myth. The coins were only 'backed' by the value of the metals themselves (through the simple expedient of melting them down
), but they were always worth *more* than the metals they were made of. This fact is witnessed to by the adulteration of the precious metal content in pretty much all currencies over time; the rulers bothered to reduce the metal content because the actual value of coins as coins was actually separate from the metal the coins were made of, that idea would not work otherwise.
As to why the Dwarves in DF should want to use money... assuming the economy is turned on, and they are allowed to buy jewelry, clothes, and personal items from other dwarves, visitors, merchants and the fortress itself, money can fill in the gaps of barter trading (if a dwarf's spare craft they are bartering away is worth 120 and they want something that costs 160, they fill in the gap with a few coins, with some variable amount of coins between 0-40 traded based on the bartering and appraisal skill of the dwarf they are trading with). To incentive the player to introduce money, the dwarves could get positive thoughts from trades that are nearly even on value (thanks to coins smoothing out the difference), and negative thoughts on heavily skewed trades or trades that are stopped because they are too uneven and their is nothing to facilitate the exchange (because the player failed to make money).
The economy as I envision it is not 'switched on' or 'switched off', if we can simply switch the economy off and have everything function fine we are better off NOT wasting the development time on ever adding the economy at all. It becomes a decision that is motivated by pure ideology and about dictating how dwarf society should run according to our sensibilities rather than furthering the actual development of the game according to the actual economic situation and ideology IN the game. In my vision bits of 'economy' are 'switched on' piecemeal in the game *by* the player, when it makes sense for the player to do so; it should not just happen automatically because of some code in the game.
Goods in barter are not worth numerical values in the fashion you refer to; that items presently have a pseudo money value attached to them when being bartered is part of what is broken about the Status Quo. Goods in barter are ranked by quality (X item is a better example of it's kind Y item, so I will trade X item away if it is a means to get Y item ), they are ranked by necessity (I need to eat more than I need my jewels, I can trade away my jewels) and they are ranked by need (I need one shirt, I do not need 100 shirts, so I can trade away 99 of my shirts).
To put it numerical terms (since everything in a computer has to be), bartered items has a separate quality value (used against other items of the same type), a necessity value (used against items less essential) and a demand value (used against items that are surplus).
I think another incentive for the player to start making and using money would be for dwarves to get positive thoughts from storing excess value/productivity they've earned as money and negative thoughts if they've done work they think should be further rewarded but have no way of receiving that reward (if the player refuses to activate the economy and/or refuses to mint/issue money). This is sort of like what GoblinCookie is suggesting with once all their basic needs are met, dwarves start wanting to acquire money (as a safety net, as a way of getting what they've earned, etc.).
I was not talking about individual dwarves, I was talking about large abstract sites. While you could make individual dwarves work that way, it would depend upon demands being modeled in a certain way (so I feed them, *then* they want clothes) rather than (they want food *and* clothes at the same times).
The player wants to get money because they want to pay people that demand money and the want to buy things from people who demand money in return; the player's dwarves want money for the exact same reason the player wants money. The value of the money is not based upon the player's own dwarves, it is based upon the wider worlds demand for money; you do not rent rooms to your dwarves as you used to because the ECONOMY SAYS YOU MUST, you rent out rooms only if your dwarves for whatever reason are sitting on a pile of money and you want to get it off them because money has some value to your fortress.
The AI on the other hand stacks up money as the lowest item in terms of
necessity value (refer back to previous quote) and keeps creating new demands for money every time the previous stack's total demand is met. So in effect we have an ultimately worthless item that they will trade for everything else but also that they demand in infinite quantities. If a site has a surplus of everything it needs but still does not have any needs at present, that site will put it's effort to obtaining money and trade away all it's *surplus* items for money.
That means that they will trade all their surplus items away to get money; so money is valuable for the player (and his dwarves) to possess. Yet if there are any items lower in the list than money (all the non-money items have a finite demand) they will trade ultimately all their money away to get those items. This by the way means inflation can be modeled, if a lot of parties are sitting on a lot of money then this drives up the prices of anything they actually want other than more money.
Note a lot of the problems of the old system from 40d version: https://dwarffortresswiki.org/index.php/40d:Dwarven_economy
Among other problems: food and rooms were not adjusted according to supply and demand, but rather set on a fixed rate based on value (and as I mentioned earlier in this post, the current Value calculation gives a big multiplier based on quality), which in turn led to dwarves being priced out of good food and rooms and sending them into massive debt. I think both the value calculation needs a rework, and it needs to act as only the first step in a supply/demand calculation (which can be done emergently be allowing dwarves to recursively bid, or done via global checks on supply).
I think the steps I propose could encompass multiple types of player fortresses (communist fortresses with a high UBI and workshops not put up for sale/rent or the economy kept only at partial activation. Capitalistic Fortresses with all of the rooms and workshops going on sale. Feudalistic fortresses (by editing the raws to grant nobles rights over workshops and farm plots), where the means of production are owned by nobles who rent them out and make money from an underclass that way). The key from a play standpoint is making sure the player is rewarded/incentived and that basic supply/demand rules are used to keep prices and costs in a reasonable range for the dwarves.
No, the old economy was a bad idea inherently; I am not interested in better versions of said bad idea. Even the best implemented version of the old economy still works on the assumption of having some magical transformation overhaul the whole society to the worse for no discernible purpose and more importantly with no conflict involved in the process.
Also prices are not set by supply+demand in reality and do not really have much role in the actual functioning of the economy either (the only exception here is the supply OF money). Pretty much the only function prices have is negative, they fail to inhibit the functioning of the economy (successful economy) or they directly interfere with the functioning of the economy (failed economy). They don't really do anything positive at all, they are basically a side effect of the demand for money and money in some strange loop feeds on it's own demand.