Honestly, I really just don't think the current supply/demand system works well AT ALL. It's incredibly convoluted, counter-intuitive, and punishing.
What I really wish they'd do is create a system of realistic demand,have prices scale off it, and then adjust supply and demand until the model gives them the prices they want. This is more complicated for them, but simpler for the player, and also more effective in the long run.
Example. Each station starts with 0 demand for Painite, paying 90k each. Every day, that demand increases by, say, 10000, and for every 10000 higher it gets, the price increases by 10%. Other stuff like BGS state could also impact demand. This demand is shared between ALL players; no weird adjustments that make demand PARTIALLY scale among players.
From that point on, the ONLY thing that effects the price would be player interaction. Players sell a lot of painite there? It quickly bottoms out. Nobody trades there for a few months? The price can get really high.
If nobody is mining a given resource, the prices for that resource would naturally climb and climb and climb, until it IS worth mining.
The best part? If you see a price that's like 900k/each for platinum, you could just look directly at the Demand and know EXACTLY how much you'll get for it. At that price it'll probably have something like 200k demand, so your entire load of 796 platinum will only reduce the total price by about 1%.