Crafty's right. When you purchase something it is an accrued expense. This means your income statement isn't billed until you have used it. But you are right there is a cash flow statement, but you do realized accrued expenses are a contra account and so you have more assets in the form of Value os Supplies. This has 0 indication on your corps well being, If you say, bought a year supply of material one day let that be your expense then you will have one day of crushing losses and 11 months of amazing profits. That doesn't make any sense, you have assets, they aren't losses.
I mean I could be wrong, but I think this is how it works. You have Surplus-Nuetral-Shortage. If we reset everything to the base price, which you can find when you buy products directly, then if in surplus the price will fall relative to the base price, if even it will freeze, if shortage it will rise. The level of the surplus/shortage or even the level of how nuetral something is is irrelevant when tracking price changes. <- I'm not saying it isn't important. Anyyway you look at it the price change will be minor. So as the price changes it will become more profitable in corps with shortages and more costly for those in surplus. The following month this is repeated. If a product is in shortage it will fall again, and it doesn't matter if it's short 1T units or just 1, the price is based on whether or not it is in shortage or surplus.
The grey area involved in this situation have multiple facets and things I may not agree with neccessarily. I'm not positive of the exact value but when in shortage prices increase for each month it is in shortage but will stop at twice the price, and begin fluctuating 3% up then down then up etc. I think most products are in this loop. Now as SC has taken supply vs demand into their own hands, they no longer allow us a functional trade strategy option. For us to exasberate shortages. I feel this is problematic because the market will never have these items stabilize as there can be a lack of incentive building corps in deep shortages compared to others. If we were allowed to set the market price, you would see a much more stable system in which corps can really benefit from shortages and in time eliminate those shortages.
Another conflict with this is, the marketplace does not seem salvageable, the shortages far out weigh the surpluses, and because of that even if people built towards equilibrium we would never get there. I have advocated several times to increase output or decrease input to make it more realistic but it has fell on deaf ears.
I guess this situation can be improved a bit by SC taking in a larger influence on S&D changes making the prices different. Not that any of this stuff matters that much because shortages just don't fluctuate enough. Just find out what makes money and build it. Find it what supplies or cause you problems and think about ways around them, simple