Overly High prices

There has been a problem of overly high prices in my area, and others as well I suspect. The actions of my alliance, that is, the creation of a friendly and competitive free market, have greatly reduced the prices, but I believe quite a few are stil too high. Before the creation of TRDFD, prices for many goods in our area usually ranged from 70-90 gold per piece, 90 gold being the more common. Current prices range from 20-40 gold per piece, with 40 being slightly more common. It is clear that TRDFD has done much, but I had hoped to bring prices down to average of 15, with a 10-20 price range. No doubt the free market we are building will continue to help, but I would like to do more to bring down these high prices. If you have any ideas or suggestions about what I should do, please post them here.

What could be interesting to do it's to upgrade trading post to have a range of 3 or more, then to organize in some islands near places with high prices a place to gather some ressources and to sell these ressources in this fork of prices.

You mean constructively placing our colonies to where the resources are most expensive? We already do that. It is both common sense, and neccesary, because we can't afford to purchase at such high prices, we are forced to build colonies there (like the rapid movement into a marble island, triple the towns there in a few days) and the increased supply and lowered demand reduces the prices. That is a natural occurance.