Please note that if you have currency for trades (as far as I remember you agreed on that) than you need to asses the relative value of goods/resources otherwise you cannot decide if you are making a loss or a gain (1) or if it would be better for you to buy/sell something else (2) and you cannot decide what is best for you to produce (3). For all of those 3 things you need money to make your life EASIER.
When conducting international trade, I don't need the game to assess relative value of goods or services. There are only a few things that matter:
1) Can I actually initiate and maintain the trade? If not, prices do not matter, because no matter how much money I throw at the problem, the goods cannot be picked up and delivered to me.
2) What price is the seller charging
me? This isn't dictated by the game engine in a world market way; it is dictated by what party A thinks they can get out of party B. If the UK is willing to buy my tungsten for $20 a unit, I take the offer. If the US comes along and offers me $30 a unit, I can either sell to the US
or I can maintain my trade with Britain for foreign policy reasons. This might be particularly important when it comes to factions, dominions, and neutrals. Sweden might be tempted to take Germany's offer for iron even if the Brits have a better offer because Sweden fears Germany more. Canada might be willing to trade with Britain at lower prices than the US just because they are a dominion. You might end up with the UK paying above the perceived market value for Portugal's tungsten because Portugal doesn't fear Germany enough to take her offer. What matters here isn't just "the world market has determined price X based on global supply and demand, so you have to pay it" but what two parties actually to do.
3) A third consideration is that instead of paying cash for goods, bartering may also occur. In this case, the relative monetary value of two goods on the global market isn't nearly as important as what the two countries are willing to trade. In particular, I can see Germany and Italy conducting barter trades with each other that have no relation to the value of those goods on the world market
because neither country can trade with most of the world.
Regarding consumption and wages, as I said, if tungsten or food is low in your system the "price"/"value" is fixed and it doesn't change in my system less the tungsten/food higher is the price. So, for example, if you currently earn 10,000 $ a month but there is a famine in your country, with your system 1kg of bread would cost always 4$ (and you need to add an extra layer which is rationing or your system is just crap) with my system the cost of bread can increase to 10,000 $ so in one month you can buy only 1 kg of bread.
Can you see as it's just way much simpler?
PS
We are discussing about a concept (money) that was created long, long time ago not to add complexity but to make things easier. I understand that many don't see the point but my feeling is that we are discussing about the utility of the wheel.
Are we talking about the real world or an HOI game? I am fully aware of the importance of currency in the history of trade and economics. I'm not an uneducated troll. But HOI3 is not the real world in all the ways I mentioned before. I don't anticipate some of these key mechanics changing in HOI4.
But here's the decision tree for your example:
Option A: No prices for domestic goods.
Conversation in The Secret Master Bunker said:
"Glorious Leader, there is a famine in the country."
"What's the problem?"
"Bread is in short supply. The people are starving. Dissent is increasing 0.05 a day. If we do not act, the People's Republic of Secret Masterland will collapse into anarchy!"
"Okay, increase consumer goods production to cover the loss. Send more people to work in the fields, or change our rationing to solve the problem."
"Yes, Glorious Leader."
Option B: With prices for domestic goods
Conversation in the Secret Master Bunker said:
"Glorious Leader, there is a famine in the country."
"What's the problem?"
"Bread is in short supply. The cost has risen to $10,000 per kilogram. The people are starving. Dissent is increasing 0.05 a day. If we do not act, the People's Republic of Secret Masterland will collapse into anarchy!"
"Okay, increase consumer goods production to cover the loss. Send more people to work in the fields, or change our rationing to solve the problem. Move some money around if necessary."
"Yes, Glorious Leader."
Alright, so which was easier? I submit to you that option B provided no added benefit to the game experience. It literally took longer to write because additional characters were involved. I submit that instead of making things simpler, it actually required more effort to wrestle with.
Edit:
I think you are going about it the wrong way.
The WW2 leaders ( and the player ) will ask: I want to build 1000 sherman tanks, show me what resources I need to aquire.
You instead ask: How can I most effectivly use the resources I have to produce products that are demanded on the "world market" and of high value and will net me profit. That is an interesting question, but it has little to do with a world war 2 game and more fitting in a logistics/industry simulation game where the goal is to build a profitable bussiness.
That's basically what I said earlier. It's not Vic2 where I'm trying to maximize profitability across 30 industries on a volatile world market. If I have determined that I need lots of Shermans to win the war, then I will find a way to build them
or I am really screwed because those resources do not exist at all, in which the game is probably lost.