Any reasonable study of the interactions of people ought to tell you that anything - ANY THING - is only worth what someone else will pay for. If the world were a truly "fair" place, then people who grow, say, coffee, would get the fair market price for it - i.e. the highest price anyone is willing to pay for it.
The reason this method rarely works is not because of evil buyers who are trying to screw the last penny out of the growers, it's because of the interventions of governments and organizations that attempt to manipulate the system. Think of the European Union subsidies to big euro agriculture (wine lakes, butter mountains) - paying farmers NOT to produce anything.
Same in the US. The Environmental Working Group notes that US farm subsidies totaled $104 billion over the last ten years. That represents an enormous tilt in a real global economic fair trade system. It's actually a pretty small amount in terms of the magnitude of the industry here, but it's huge leverage against foreign growers.
I guess my basic point here is that any deliberate political intervention in a system, whether by governments or by "well-meaning" activist groups inevitably screws up the concept of "fairness".