Well as any other game Entropia COST money for most players, and for MOST players it is not possible to earn money in the game and they have to rely on their deposits.
However there are possibillities to make profit. Trading is one of them, buying stuff for lower than selling them to bring it down to the point.
And as you might have noticed you can'T buy everything from the TT, so basically you try to loot stuff which is more worth to the buyer because the buyer can't get from the Trading Terminal and therefor will pay market price to other players.
Any regular activity in the main professions ( mining, hunting or crafting ) will get you less return in terms of TT value than you pay to get the loot. So you need to find stuff to loot which brings more in market value than you have been deducted for the playing. In the long term your return TT-wise will be ~90%. So you have to make the 10% from the Marketvalue of your stuff to break even.