All of this theory is nice but completely useless in the real world ( game world in this case ).A few months since posting this thread, I've come to a conclusion:
Trading fairly is not about trading at a ratio equivalent to the value of the goods in question, but about moving goods from one player to the next while establishing and maintaining a healthy network of trade partners.
In practice this requires a player to set a standard rate they aim to trade at, such as 1:1 in value. This is the most widely accepted rate as is evident throughout the forums and this thread. There's a bit more to a fair trade however, when taking into account factors such as fees, availability, demand, stock and resourcefulness.
- The fees are simply those that occur when trading with undiscovered neighbors.
- The availability of a good defines how easily it can be obtained by other players (neighbors or fellows). This is of course heavily dependant on the boosts, progress and activity of any such player.
- The demand is defined by what you need yourself, as well as the needs of other players.
- Stock is what I categorize as the amount of goods you have readily available yourself in your Main Hall.
- Lastly but not least, the most important feat: Resourcefulness. This is your ability to cope with your given situations including:
- Planning ahead to ensure you have the correct number and type of resources in stock for research, negotiating or upgrading;
- Awareness of which neighbors and fellows are active, what their boosts are and how far they have progressed;
- Aiding new players to help them progress more quickly and become solid trade partners;
- Seeking out active neighbors offering what you require and discovering them quickly.
So how do these help define a fair trade?
If a new neighbor has just entered the game and they have boosts for a good I require, then it's fair for me (being in chapter 4) to accept a trade that is not within the 1:1 ratio in value, but more expensive or carries a fee. Why? My goods production is far more advanced through relics and upgrades. I can compensate for the 'lost' 10-50 goods per trade very easily. As that neighbor progresses, the more the trade ratio should even out. That's up to you to ensure though! The advantage of having a further trade partner to add to your network should speak for itself.
So what about a player who is as advanced as I? Is it fair to accept a trade that is more beneficial to them or carries a fee? Yes, when taking into account availability, demand and stock. Should a specific good that you do not have in stock and is in high demand by other players be available by very few players, then it is fair to pay more for that specific good in such a situation. The reason is simply that the supplier will need to decrease their own progression in order to supply everyone demanding that specific good, or all other players will begin or continue to stall in their progression. Thus, if you want to continue to progress as a demanding player, you'll need to give an incentive. That is then deemed fair.
Now, what about accepting offers that are more beneficial to you as a player? Well, this is where it comes down to either the above scenario and you being the supplier, or your good will by returning the favour. Whether that respective player ends up accepting/getting your trade is another matter, but in the end that is a balanced form of trading. Offering goods cheaper than 1:1 is a great incentive to get others to engage into trading, that from my experience then become regular trade partners at the standard rate of 1:1 in value. The addition of more trading partners makes this fair, as you are gaining an advantage in the end that you didn't have before. You can also view it as an investment, but one of the best you can make in this game.
So is there a fair trade that includes a traders fee? Apart from the two mentioned above: no. Quite frankly because it's just a game mechanic to encourage players to discover each other and has nothing to do with the actual bargaining aspect among st players. In other words: I tend to only use these as indications of which undiscovered neighbors are active and then decide on whether to make the effort of discovering them based on the distance, their offers, boosts and the current availability and demand of those goods in my current network of trade partners.
And how does resourcefulness fit in? Basically this is completely player defined and therefore relies entirely on how much effort you're willing to invest into the game in terms of "strategy". If you don't care or take the time to plan how you play the game, then it's only fair if you miss out on some of the best trades and potential trade partners. Life's hard, I know. Especially for those of us who have jobs...
In my fellowship, we trade at 1:1 regardless of any other factors that would affect the cost of production. As long as the fellowship is properly balance, we don't need anybody else to get what goods we need. We encourage all members to produce only their boosted goods and to trade for the others. That way, we each produce more and gain an advantage from our own boosted goods.
The system you presented might be applicable if we had different markets for neighbors, fellowship and others. If the markets where separated in such a way, different prices could emerge for the same goods where it would be possible to exploit the differences, but I doubt the game is going to go that way.