Goods and food usually do pretty well, while rares and oil are virtually worthless after a while. I think it is because the AI's dominate the market; and AI's, well, they buy lots of infantry a very few tanks and planes. Human players have been REALLY reluctant to enter orders (as opposed to buying/selling immediatly on existing orders!) since the market fee was subtracted even if your order doesn't get processed... no one likes to pay a high percentage for a deal that may not even go through. Proof may be that the market runs almost completely dry after the last neutrals are being gobbled up.
Coal is not a game resource...?
