My point is, that the market does not work properly if you have a constant undersupply over a long time AND the long pricetrend is declining at the same time for the products that are in constant undersupply.
Rising prices would have two effects.
One would be a motive for players to build more corporations of the kind that have rising prices. You seem to say that you don't believe players will do that. I don't understand why not. I know I for one do go specifically for the products in red and barely anything but that.
The other effect of a rising price would be a falling demand. And yes, this might be due to closed corporations. That's how a free market works.
The combination of those two factors will eventually make the supply and demand ratio shift. It'll never stay balanced at perfectly zero under/oversupply, but at least it will fluctuate between them. Not stay in undersupply for ever as it is now for many goods.
Your problem is what I believe you refer to as the "roof". It needs to be removed or at least the band of that the prices move in, needs to be expanded a lot.
As to the last years effect of the changes, I can observe that it hits all my ressourceproducing corporations (oil, wood, minerals etc.). I'm not sure why all these corporations, that used to generate profit have become unprofitable.
Most industry can still do OK, except for electric companys which are hopelessly in deficit even when fully upgraded. This is also a change from some years ago.
(The above is a relative development in my countries. Actual level of profit of course depends on how well my indexes are doing etc, but that doesn't matter in this case. My countries are doing better than 20 years ago, but still these corporations are doing relatively worse. Contrary to a lot of other branches).
I'm not sure why this gradual change hits unevenly, but it may eventually become an unbalancing problem if natural ressource production is being dropped by players because they have become unprofitable.
If at some point gamedevelopment will consider an actual change to the way the market is working - rather than just make minor adjustments - it would be wonderfull to know.
I would be happy to give input for a more specific model, but only if the gate is actually open.