ok, its economics 101, sadly not taught in the schools anymore. the fair price for buying and selling any package of goods for the constructions of a GB is what the market will bear. it is what people are willing buy for. lesson: if you try to sell your goods for a million fps for the arc, lets say, and nobody buys the goods, then you have set the price too high for the market to bear. so, as a seller, you got a couple choices here. 1. raise your price from 1 million to say 2 million and see if you can get a sale. 2. keep your price the same and see if you can get a sale. 3. lower your price to a more reasonable one where someone will think its worth it to pay your lower price. as a seller, you're gonna have to keep lowering it til someone buys the goods. when someone buys your goods, THEN and only THEN will you have a fair trade. to put it in perspective, the only "fair" price is the one agreed upon by 2 people. this then, is the economic side of the game. many people dont like this side of the game because they dont understand it. people run from economics. instead, embrace it and you'll find the game a lot more to your liking. so your basic question of what is a fair trade ends up being one where you think its worth it. and if you think the price is STILL too high, then build the goods production and make the goods yourself, its not impossible...unless you want instant gratification instantly.