This may not seem relevant now, but those of you who have played RT know that the current supply of consumer good is a rare thing. Very few miners coose to go the CG route since tax miners and mineral miners are often more profitable.
Here is my suggestion: Instead of caping the price at 4 and reselling at 5, create a dynamic system instead. Each player can set the price at which CGs are resold to their population. But for every dollar they raise the price, the consumption rate of goods within their empire drops. This would allow Miners to sell CGs at prices higher than 4, creating a more competitive market, and making CGs a much more profitable route to take.
K
KusariOP