That is what I'm trying to say coffee, that prices should be equally stable across 2p through to 8p games.

Sort of related to previous stockpile suggestions.

I think it would be quite effective to introduce an abstract value that essentially represents the markets stockpile, but can go into the negative. The idea would be that the market would have a 'desired stockpile' amount for each commodity, whenever the stockpile in the market is below that amount the price would be high, if it is above prices would be lower. The desired stockpile number would rise for a commodity when the actual amount in the market drops below zero, and lower when the amount in the market is over zero.

As a result of this if there is a large run on, lets say water, and players are buying at a much higher rate than they are selling, so the market stockpile goes negative, and stays there; the desired stockpile may raise from 1000 to about 10,000. The price of the water would remain high until the actual stockpile gets over the desired stockpile. In cases of larger runs on the market where the stockpile stays in negative numbers for longer the desired stockpile would go to a higher number, essentially increasing the amount of resources it takes to lower the price.

This would effectively make the market naturally stabilise to the volume of transactions, without requiring the number of players to be taken into account.

That may be the case in some games but not on average. On average in 8p games there will be very closely 4x more demand for resources than in 2p games. What company people pick only affects on which goods the most demand is made. Lop sided games ar the exception not the rule. 

I don't think it makes gameplay sense for the game to have extremely different market stability between 2p games and 8p games. 

I also suggested to make higher volume goods (Water, iron, aluminium, carbon, silicon and power) to be 2x or even 4x more stable compared to other goods because these resources can be easily mass produced.

I think we can take current state of price mobiity to be the default position for 4p games, and make prices 2x more mobile for 2p games, and 2x less mobile for 8p games. Additionally, the prices of high volume resources (ie. mineables) become 2x less mobile whereas everything else stays the same.

I'd like to see price volatility itself be a variable that can be predicted (or, under time pressure, roughly estimated) by a player who is paying attention to the relevant factors. So that instead of saying "A 2p game will have slowly-varying prices and an 8p game will have wildly-swinging prices", we'd be able to assess the price volatility of individual resources at specific times and circumstances.

Consider this as a simple example:

Price volatility is dependent on trade volume. Heavily-traded resources are stable, thinly-traded resources are volatile. Recent volume is weighted more heavily than past volume. (This is basically what Nuclear_Wessels has suggested, although the mechanism may be a little different.)

Here's how that would play out:

If demand outstrips supply, the price rises, and vice versa, just like normal. But now "spikiness" matters. As long as demand and production stay close to each other, the price will smoothly rise (if it's being underproduced or demand is rising) and smoothly fall (if it's being overproduced or demand is falling). You can make a handsome profit by shifting into a high-priced industry and know that the high price will be sustainable for long enough to pay off your initial investment. But if there's a sharp swing in demand, or supply - or if someone starts dumping a big stockpile, or buying a big stockpile, then the price can shift rapidly, which invites opportunities for huge windfalls (if you time it right and are on the right side of the trade) and huge disasters (if you time it wrong or are on the wrong side of the trade).

The market that we have now kind of works like that, except that price stability depends on there being roughly equal supply and demand. Higher balanced trade volumes are more price-stable than lower balanced trade volumes, but imbalanced trade is the opposite - higher volumes in a rising (or falling) market mean a faster rise (or fall), lower volumes mean a slower rise or fall. This makes prices very chaotic, which in turn makes it hard to predict future profitable opportunities, and hard to capitalize on them when they appear.

Now, to some degree you want that to be hard. That's where the gameplay is. People who are better at that kind of prediction should have an edge in the game. But there's a line between "hard to predict" and "impossible to predict", and I think the chaos from the current pricing mechanism is on the wrong side of that line. The game is complicated enough that even if the price mechanism lends itself towards relatively easy predictions, people's brains will still be so taxed just keeping up with everything going on that the game won't lose its competitiveness.

I would argue that the prices are extremely immobile. If the prices were more mobile then we would not have the standard build of aluminum+steel through the first upgrade and add glass+power through the second. If prices were more mobile and no one sold food then anyone who did not produce food through the first 5 mins of the game would be deeply in debt.

As it currently stands the prices are so inflexible that is it suicidal to produce only basic resources and use cash to upgrade.