I think the market and it's shifting will be based more upon the total changes in supply made in a system by the players/NPC's. So imagine if you check a market board and it says Titanium is going for 3000 credits a ton and you make a huge run with 20 tons of titanium in your nifty little freelancer and make a tidy profit off of it. Now that you've injected a large amount of titanium into the systems market I bet the price will shift for anyone else bringing it in. Now I'm willing to bet planets will have different rates of consumption for different products and this will mean they are relatively safe bets for running specific cargo to, but if it gets inundated with the high value product I bet the price will drop for an amount of time equal to the time it takes the planets consumption rate to push the price back up. I think this would be great because it WOULD allow us to manipulate it to some degree, but it wouldn't allow us to totally shift the market in an EVE style shitstorm. Of course this is just what I like and think would be complex, without giving us all carpal tunnel from editing our spreadsheets.