How many railroads do you need to supply your 6-7 steel plants and 4 tank factories as USSR?
In reality you don`t really need "decent" infrastructure if your production is concentrated. You just need to build specific rails to the production sites, which is a very minor part of what "infrastructure" should be for people convenience.
There are also places like Norilsk, that used planes to move important people in and out, and ships to move in the supplies and production by river, and outside the city, there is over 500km of tundra with next to nobody.
So, no, infrastructure specific to extraction of goods should rather be accounted in the cost of extraction facility, not the other way around where the cost of the extraction facility is accounted in infrastructure cost.
Podcat had already stated that they were thinking about adding "concentrated" bonuses into the game for that specific reason, because it frees up manpower and industry needs, thus "efficiency" is improved.
Both Germany and USSR invested 10,000's of railroad kilometers to extract resources from their territories, and Germany had to actually setup a priority system because there simply wasn't enough infrastructure to move all resources and troops. That is a direct limit on the amount of resources Germany was able to extract because they cannot move it all.
And no where did I say that this would allow you to "build" your way out of the war... IF you produce 50% with 0 infrastructure, you would have to spend the resources to build the entire region's infrastructure up 1 to gain a 3.33% bonus per level... That may not even be worth it to the player.
IF we modelled the cost of extraction, infrastructure would play a key role in this, as lower levels of infrastructure would only allow mules/trucks instead of trains.
To give a current example, grain processing companies here in the US have been importing grain from Kazakistan this year instead of getting the same grains from Canada. There is so much traffic in the Midwest US that train car deliveries are months behind schedule. That is a real world cost due to lack of infrastructure where grain is rotting in the fields/ storage because there simply isn't enough infrastructure available to move it. IF resources used the supply lines as well and didn't just magically appear in your stockpile, then this would be realized in the game.